Did what I needed to do to get d3 to not be loaded during play: refactored the ladder views out of the play wad, and got the Router to handle viewClass being a string rather than a fully loaded module.

app/core/ModuleLoader.coffee

@@ -59,15 +59,25 @@ module.exports = ModuleLoader = class ModuleLoader extends CocoClass
 
   onFileLoad: (e) =>
     $("#module-loading-list li[data-path='#{e.item.id}']").removeClass('loading').addClass('success')
-    have = window.require.list()
-    console.group('Dependencies', e.item.id) if LOG
-    @recentLoadedBytes += e.rawResult.length
-    dependencies = @parseDependencies(e.rawResult)
-    console.groupEnd() if LOG
-    missing = _.difference dependencies, have
-    @load(module, false) for module in missing
-    locale.update() if _.string.startsWith(e.item.id, 'locale')
+
+    # load dependencies if it's not a vendor library
+    if not _.string.startsWith(e.item.id, 'vendor')
+      have = window.require.list()
+      console.group('Dependencies', e.item.id) if LOG
+      @recentLoadedBytes += e.rawResult.length
+      dependencies = @parseDependencies(e.rawResult)
+      console.groupEnd() if LOG
+      missing = _.difference dependencies, have
+      @load(module, false) for module in missing
+
+    # update locale data
+    if _.string.startsWith(e.item.id, 'locale')
+      locale.update()
+      
+    # just a bit of cleanup to get the script objects out of the body element
     $(e.result).remove()
+    
+    # a module and its dependencies have loaded!
     if @queue.progress is 1
       $('#module-loading-list').modal('hide')
       @recentPaths.sort()
@@ -96,6 +106,7 @@ module.exports = ModuleLoader = class ModuleLoader extends CocoClass
     console.groupEnd() if LOG
     return dependencies
 
+  # basically ripped out of commonjs definition
   expand: (root, name) ->
     results = []
     if /^\.\.?(\/|$)/.test(name)

app/core/Router.coffee

@@ -84,8 +84,8 @@ module.exports = class CocoRouter extends Backbone.Router
 
     'play-old': go('play/MainPlayView')  # This used to be 'play'.
     'play': go('play/WorldMapView')
-    'play/ladder/:levelID': go('play/ladder/LadderView')
-    'play/ladder': go('play/ladder/MainLadderView')
+    'play/ladder/:levelID': go('ladder/LadderView')
+    'play/ladder': go('ladder/MainLadderView')
     'play/level/:levelID': go('play/level/PlayLevelView')
     'play/spectate/:levelID': go('play/SpectateView')
     'play/:map': go('play/WorldMapView')
@@ -185,6 +185,14 @@ module.exports = class CocoRouter extends Backbone.Router
     window.tracker?.trackPageView()
 
   onNavigate: (e) ->
+    if _.isString e.viewClass
+      ViewClass = @tryToLoadModule e.viewClass
+      if not ViewClass and application.moduleLoader.load(e.viewClass)
+        @listenToOnce application.moduleLoader, 'load-complete', ->
+          @onNavigate(e)
+        return
+      e.viewClass = ViewClass
+
     manualView = e.view or e.viewClass
     if (e.route is document.location.pathname) and not manualView
       return document.location.reload()

app/lib/LevelSetupManager.coffee

@@ -89,8 +89,8 @@ module.exports = class LevelSetupManager extends CocoClass
 
   onInventoryModalPlayClicked: ->
     @navigatingToPlay = true
-    PlayLevelView = require 'views/play/level/PlayLevelView'
-    LadderView = require 'views/play/ladder/LadderView'
+    PlayLevelView = 'views/play/level/PlayLevelView'
+    LadderView = 'views/ladder/LadderView'
     viewClass = if @options.levelPath is 'ladder' then LadderView else PlayLevelView
     Backbone.Mediator.publish 'router:navigate', {
       route: "/play/#{@options.levelPath || 'level'}/#{@options.levelID}"

app/schemas/subscriptions/misc.coffee

@@ -35,7 +35,7 @@ module.exports =
   'router:navigate': c.object {required: ['route']},
     route: {type: 'string'}
     view: {type: 'object'}
-    viewClass: {type: 'function'}
+    viewClass: {type: ['function', 'string']}
     viewArgs: {type: 'array'}
 
   'router:navigated': c.object {required: ['route']},

app/views/editor/DeltaView.coffee

@@ -1,6 +1,8 @@
 CocoView = require 'views/core/CocoView'
 template = require 'templates/editor/delta'
 deltasLib = require 'core/deltas'
+require 'vendor/diffview'
+require 'vendor/difflib'
 
 TEXTDIFF_OPTIONS =
   baseTextName: "Old"

app/views/editor/level/LevelEditView.coffee

@@ -26,6 +26,8 @@ SystemsDocumentationView = require 'views/editor/docs/SystemsDocumentationView'
 LevelFeedbackView = require 'views/editor/level/LevelFeedbackView'
 storage = require 'core/storage'
 
+require 'vendor/coffeescript' # this is tenuous, since the LevelSession and LevelComponent models are what compile the code
+
 module.exports = class LevelEditView extends RootView
   id: 'editor-level-view'
   className: 'editor'

app/views/ladder/LadderView.coffee

@@ -55,7 +55,7 @@ module.exports = class LadderView extends RootView
     ctx._ = _
     if tournamentDate = {greed: 1402444800000, 'criss-cross': 1410912000000}[@levelID]
       ctx.tournamentTimeLeft = moment(new Date(tournamentDate)).fromNow()
-    ctx.winners = require('views/play/ladder/tournament_results')[@levelID]
+    ctx.winners = require('./tournament_results')[@levelID]
     ctx
 
   afterRender: ->

app/views/play/level/ControlBarView.coffee

@@ -63,18 +63,18 @@ module.exports = class ControlBarView extends CocoView
     if @level.get('type', true) in ['ladder', 'ladder-tutorial', 'hero-ladder']
       levelID = @level.get('slug').replace /\-tutorial$/, ''
       @homeLink = c.homeLink = '/play/ladder/' + levelID
-      @homeViewClass = require 'views/play/ladder/LadderView'
+      @homeViewClass = 'views/ladder/LadderView'
       @homeViewArgs.push levelID
     else if @level.get('type', true) in ['hero', 'hero-coop']
       @homeLink = c.homeLink = '/play'
-      @homeViewClass = require 'views/play/WorldMapView'
+      @homeViewClass = 'views/play/WorldMapView'
       campaign = CampaignOptions.getCampaignForSlug @level.get 'slug'
       if campaign isnt 'dungeon'
         @homeLink += '/' + campaign
         @homeViewArgs.push campaign
     else
       @homeLink = c.homeLink = '/'
-      @homeViewClass = require 'views/HomeView'
+      @homeViewClass = 'views/HomeView'
     c.editorLink = "/editor/level/#{@level.get('slug')}"
     c.homeLink = @homeLink
     c

app/views/play/level/PlayLevelView.coffee

@@ -340,6 +340,7 @@ module.exports = class PlayLevelView extends RootView
     application.tracker?.trackEvent 'Started Level', category:'Play Level', levelID: @levelID
 
   playAmbientSound: ->
+    return if @destroyed
     return if @ambientSound
     return unless file = {Dungeon: 'ambient-dungeon', Grass: 'ambient-grass'}[@level.get('terrain')]
     src = "/file/interface/#{file}#{AudioPlayer.ext}"

app/views/play/level/modal/HeroVictoryModal.coffee

@@ -260,7 +260,7 @@ module.exports = class HeroVictoryModal extends ModalView
   onGameSubmitted: (e) ->
     ladderURL = "/play/ladder/#{@level.get('slug')}#my-matches"
     # Preserve the supermodel as we navigate back to the ladder.
-    Backbone.Mediator.publish 'router:navigate', route: ladderURL, viewClass: require('views/play/ladder/LadderView'), viewArgs: [{supermodel: @supermodel}, @level.get('slug')]
+    Backbone.Mediator.publish 'router:navigate', route: ladderURL, viewClass: 'views/ladder/LadderView', viewArgs: [{supermodel: @supermodel}, @level.get('slug')]
 
   playSelectionSound: (hero, preload=false) ->
     return unless sounds = hero.get('soundTriggers')?.selected
@@ -324,4 +324,4 @@ module.exports = class HeroVictoryModal extends ModalView
     e.preventDefault()
     route = $(e.target).data('href')
     # Preserve the supermodel as we navigate back to the ladder.
-    Backbone.Mediator.publish 'router:navigate', route: route, viewClass: require('views/play/ladder/LadderView'), viewArgs: [{supermodel: if @options.hasReceivedMemoryWarning then null else @supermodel}, @level.get('slug')]
+    Backbone.Mediator.publish 'router:navigate', route: route, viewClass: 'views/ladder/LadderView', viewArgs: [{supermodel: if @options.hasReceivedMemoryWarning then null else @supermodel}, @level.get('slug')]

config.coffee

@@ -63,8 +63,8 @@ exports.config =
 
         #- vendor.js, all the vendor libraries
         'javascripts/vendor.js': [
-          regJoin('^vendor/(?!scripts/Box2d)')
-          regJoin('^bower_components/(?!(aether|d3))')
+          regJoin('^vendor/scripts/(?!(Box2d|coffeescript))')
+          regJoin('^bower_components/(?!(aether|d3|difflib|diffview))')
         ]
         
         #- Other vendor libraries in separate bunches
@@ -78,6 +78,9 @@ exports.config =
         
         # Any vendor libraries we don't want the client to load immediately
         'javascripts/app/vendor/d3.js': regJoin('^bower_components/d3')
+        'javascripts/app/vendor/coffeescript.js': 'vendor/scripts/coffeescript.js'
+        'javascripts/app/vendor/difflib.js': 'vendor/scripts/difflib.js'
+        'javascripts/app/vendor/diffview.js': 'vendor/scripts/diffview.js'
         
         #- test, demo libraries
         'javascripts/test-app.js': regJoin('^test/app/')