Switching from fantasy to science fiction/science fantasy you run into issues with deadliness, firearms, automatic weapons and the whole panoply of high tech gizmoes, gadgets, sights, bullets and so on and so forth.
You also have to account for more advanced forms of protection while not overdoing the whiff factor or making it too easy to hurt someone the other way.
This ain’t easy.
I haven’t quite decided yet but I’m leaning towards damage reduction for armour and armour class boosting for force-shields/agility. Force shields won’t apply to melee attacks and ranged attacks should find it easier to hit,
I want to keep things as simple as possible but I also want combat to have plenty of options and to have a universal guideline so players can easily decide what they want to try. Sticking with LotFPs attack guidelines, mostly, this also gives fighters (soldiers) a much greater capacity to pull special attack moves.
Something like a universal -5 penalty no matter if you’re tripping, headshotting, disarming or any other environmental or competency issues. You could then offset that penalty – and even turn it into a bonus – by taking lots of skill levels.
The spirit of ‘old school’ is heavy on the improvisation but by providing a framework you can enable a lot of improvisation from that.
“What’s the penalty for fighting in zero gee?”
“When I levelled last time, I took Zero gee combat once.”
Bosh, sorted and fighters/soldiers become a damn sight more interesting all of a sudden :)