I don't play CoD so i don't know quite what you mean but even a playlist that new players have to play in for a certain period of time would be cool.
I don't think it's possible. The call of duty AI can't even jump. Halo is much, much more complicated than Call of Duty, so developing decent MP AI would be nigh on impossible.
the call of duty bots are basically an aimbot with a random number generator, to determine when they shoot you; this wouldn't work in Halo, especially if they were to add in Forgemaps.
No, I don't know if you noticed, but there is a little thing called firefight. Try it, it is like combay training, but Halo-er.