Hmm.. I know this sounds cheap.. but the Y2K3 mod does almost everything mentioned here, and replaced BIS's soldiers, vehicles etc (Most of them), new sounds, good tracer scripts etc..
And you can play most misisons and the imporoments still work!
(The swimming happens when you eject out a plane/helo as a pilot over water.. With full combat gear, your closer to a rock, really)
On a slightly less releated matter, the PLA (or is it VME?) addon pack adds soldiers (Using both new and one set is BIS models) with, well, after playing online coop with a friend, "fairly scarey AI"..
For example, if they can't shot you, tanks will shell your location. They appered to destoy they're own vehicles if you kill all the people in it, if you shoot the gunner on a fixed gun (Say a anti-air gun), the command gets in as gunner etc... It is acctualy scarey
(Even on a simple misison where you have to cross that bridge in Nogava...)
While using Y2K3 and PLA units flashpoint becomes even better (IMO, Gandalf agrees.. violently
), and in a lot of respects more realistic..
Okay so the addons for that misison were over 500mb, but that's no the point..
Maybe you could join togeter some of the AI enchancement scripts, write others, modify them, make a "Apply to all soldiers on map" type thing (So it's very easy to use). And it would be very impressive
Probobaly better sleep now..
- Ben