In 40k, shooting and melee is determined with 3 dice rolls - to hit, to wound, to save.
My plan would be to combine at least 2 of these rolls into one, using custom dice. I've also introduced a Glance result, which does not wound, but incapacitates (same as a knock-down in BB).
For example:
A 'combat' die has 6 faces - Miss, Miss/Glance, Glance, Glance/Hit, Hit, Hit/Miss
Number of shots is determined by number of dice thrown.
Skill and difficulty (cover, movement, flying target etc) are determined by either:
a) rolling more or fewer dice and choosing the best (attacker has advantage) or choosing the worst (defender has advantage).
b) rerolling dice (choice dependant on attacker or defender advantage) - this works better for when a whole unit shoots.
Different weapons can affect the result on the combination results - e.g. An Explosive weapon Hits on a Miss/Hit, Armour Piercing Hits on Glance/Hit, Concussive weapons Glance on a Miss/Glance. Different weapons can have more than one of these attributes.
Different armours also have an affect - Flak Jacket Glances on Glance/Hit, Stabilising System Misses on a Miss/Glance (representing the extra difficulty in stunning the bearer), Heavy armour Misses on a Miss/Hit. Different armours can have more than one of these attributes.
Not sure what to do on a combination result if a) neither weapon or armour affects the result or b) both do.