Well, given that basic AI performance is set in the .plr file then tweaked by .aiw and .rcd files I found that different installs for different car types works well. So one install for, oddly enough, GT cars; another for C-Era, ALMS, and LMP style cars; another for formula cars; another for touring cars; and, of course, P&G for '50's through '70's sport cars. All reference a common locations folder (so unfortunately all see P&G LOD screens). This also makes talent files easier to deal with since less overlap.