For Pathfinder, as mentioned in the comments above, Crossbow Mastery is pretty useful. Otherwise, as far as feats go, you've got 'em covered.
The Far Shot feat will turn the -2 range increment penalties into -1, which can be very useful to shoot from long range.
Here's where some cheese comes in-- when you take a 1-level dip in Rogue with the Sniper Archetype, you gain the Accuracy ability, which that further by half. This does stack RAW, which effectively doubles your range increment distance before you even see a penalty. For example, you can pick stuff off from almost half a mile away with only a -4 penalty. Granted, you'd need scrying or something to spot your targets, but your stealth check gets hilarious... Your GM will probably scowl at you for this. Pay him back by taking Leadership and Siege Engine feats... and chuck donkeys at the BBEG from the next county. On a more serious note, the Ballista is good and can be used every turn like this.
If your GM allows material from 3.5e, then you can take both Crossbow Sniper and Improved Crossbow Sniper. The former grants you half your Dex modifier to damage and a +30 feet to Sneak Attack and Skirmish ranges, and the latter bumps it up to full dex and an additional 30 feet. Furthermore, a 1-level dip in Rogue grants you a Sneak Attack, and the Craven feat from 3.5 will grant you your character level as bonus damage to SAs (at the cost of -2 will saves against fear effects).
If your GM will allow things from 3.0, you can attach a Gnome Crossbow Sight to your xbows to ignore the first two range increment penalties.
As a GM, I allow pretty much all things regarding crossbows in Pathfinder, because they're already such a sub-optimal weapon compared to bows, thanks to the absence of the strength modifier to damage and manyshot. You'll probably be using the Launching Crossbow as an Alchemist, so your experience won't be as bad as most classes, but the feat tax for using any crossbow is almost ridiculously heavy.
A little bit more cheese, but if you take a 1-level dip in Oracle, choose the Waves mystery, and take Water Sight as your first-level revelation, you'll be able to lay down Obscuring Mist a few times a day and be able to see through it without penalty. Being able to shoot with guaranteed total concealment is a huge plus to tactical fighting (its the basis for my Sniper using crossbows in my current PF game, in fact, since the concealment guarantees Sneak Attacks)
