Second, talking about long range fighters... Some seriously big penalty to sneak while using/holding biggun would suit the situation and furthermore would prevent from making sneaking overpowered as it was before.
c) moving when sneaked costs 1 ap/hex; can't move if at 0 ap - silent run would allow you to make quick, short leaps but in general you wouldn't be able to move around too muchf) using skills, items and attacks unsneaks you
Sneak:Make different fomulas for mobs and players. The same formula to sneak up to player as now, but easier for critters. I mean, you don't need 300% sneak to get to harmless gecko, who will see you in 3 hexes anyway. Make no min. range for critters and a bit easier formula, so with 150% sneak you can sneak up from the back to most low leveled critters.