Seriously, what's wrong with it? Just make it so that big guns demand high strength and there's no way around it. When there's no big guns around, big gunners would prefer other burst weapons and shotguns. Energy weapons wouldn't even have to have a class dedicated for them because energy weps would be top tier weapons which everyone would want. This would demand overhaul of profesions and how guns were available, but hell, it would definitely bring cool benefits.
I made this kind of modification in fallout tactics and it effing rocked.
This idea actually requires a lot less tinkering than I thought it did. All weapon protos or whatever would just be changed to use 'Small Guns' for their skill rolls instead of Big Guns, but Small Guns would be renamed 'Firearms' in all the menus, etc.
Holy shit, and melee weapons/unarmed weapons/throwing could all use the same skill to determine to hit chance as well. They could just be registered ingame as using the melee skill, and that gets renamed 'Low Tech'.
I don't think it'd be possible to combine lockpick/traps, but at least the weapon system could be improved.
It would, at the very least, make the game more 'fun'. If you find a gun, any gun, you can start blasting away. And if melee and unarmed were the same skill, people would be a lot more likely to invest a couple skills points in it.