Yes; after exporting it from Brawlbox, use Autodesk's FBX Converter 2013.3 to convert the .dae to .fbx, then import the fbx into Blender
Make sure that you use the latest version of Blender. Edit the model in Blender; don't worry about the bones looking like they're in really weird positions; in fact, they must be this way in order for the rigging to be properly imported
Now export from Blender as a .fbx with default settings, use FBX Converter to convert that to a .dae, import that with Brawlbox .77, and export it from there as a .mdl0
Now open up the character the model is going over in Brawlbox .71, use the Add New Object button to import each polygon individually from the MDL0, and then delete the pre-existing fighter's polygons so that only your character is left; Make sure that you have Merge Models UNchecked when you're importing each individual polygon
Source: Me, the first person ever to master Blender to Brawl importing
Post Merge: April 11, 2017, 02:35:54 PM
P.S. You can use you're pre-existing model, too! Just unparent the model from the current bones, remove the current modifier, import the fbx skeleton, and then reparent the model to that skeleton!