Heyyo,
Yeah, I think it's a pretty nice idea, cause it does encourage more teamplay like CS was meant to be.
But, there should also be important defense areas bots can cover. A good example is on DE_Dust, in the upper tunnels, if the CT's get in there, from the 3 sides closest to the CT spawn point, and the bomb site, they can own almost all the T's that come in, so they don't even get close to the bombsites. But I'm just thinkin' out loud, cause your idea should get the job done nicely.