Time for MS to allow users to build 360 game mods

I really would like the idea of building my own oblivion dungeons, Halo 2 maps,  or even Prey levels, but on a console this is pretty much not a viable option, even tho there is one successful game with a level builder on the 360, Far Cry  Predator, but how about even sell or offer for free a PC download that we can build game levels for our 360s and upload to a web site and then try it on our 360s.

this could be even easier with simple keyboard/mouse support and have the games come with the software already. I do not want to wait a full generation before building levels for my console games, I do not want to just build them on the PC, it is time Microsoft to  give us the ability, now  hurry up with it.