The old saying applies: If you want something done and it's simple enough, make a PR.
Though, cpw/Lex are only accepting 1.7 PRs unless it's important enough.
@loordgek shut up, there's 965 and that's usable.
@OP I recommend direwolf20's video for running multiple modded mc versions in parallel, it's in the eaq.
Launcher works on "profiles" and "versions".
To launch Forge, we need to hack the "version" file. This is done by copying the "version" file and hacking the copy.
We then copy the forge jar in as a library, as well as what forge needs.
Lastly, another "profile" is made which allows you to just start modded minecraft using it.
The launcher is supposed to mount .minecraft/assets/virtual/legacy as the assets folder. I'm sticking to my guns and saying your launcher needs an update.