I would actually remove Dex from damage on ranged attacks unless thrown/hurled by muscle power and go back to bows adding Strength to damage.
As for crossbows, well, they've suffered a lot in D&D, so if you want to keep the loading property, they should have dramatically boosted damage (especially if you remove Dex from the equation). At close ranges, the power of a crossbow can be devastating (a real crossbow, not that cheap one-handed toy, lol). Another thing that is usually forgotten (save in 4e, ironically), is that crossbows are very accurate weapons; never underestimate the advantage of an iron sight!
The game should make crossbows an alternative to bows, not their poor cousin, alas, the bow has been enshrined in D&D since forever...but that's a personal rant, lol, so I'll stop now.