Well if you are looking for less assistance, the only way I can think of to go about it is to either find a manual rack that feels just fantastic (Flaming River maybe?) or go electric. Are you looking to reduce resistance all the time? I know some setups can get pretty sophisticated, altering resistance based on vechile speed, or steering wheel angle, etc. I'm not sure what's out there for aftermarket kits, you may have to snag something off of another vehicle like you suggested.
I'm not all that familiar with hydroboost, maybe someone here is - I know it's for brakes, but it combines power steering and brakes, uses the pressure from power steering to assist the brakes. There might be some configuration there that you can tinker with, maybe less pressure on the power steering side and more on the brake side or something, I don't know, but it might be worth looking into. Plus Ford used hydroboost on cars, so maybe a retrofit wouldn't be that bad? I don't know, just throwing ideas out there.