Why not?!
First, of course, we need at least Rogue 6 for Int modifier to Crossbow damage.
Also, I find the 19 Dex required for IPS to be onerous. If Kensai and the Fighter Specialization Enhancements were better fitted to ranged weapons (giving +2 Damage each instead of +1) maybe we could aim for a 17 Dex (+2 Tome) and manually pick up IPS and go Kensai, but let's just let Ranger do it for us and get a bunch of nice freebies and Favored Enemies thrown in too. Might as well take Deepwood Sniper, and then be set up for Deepwood Sniper II if that ever decides to show up.
So that leaves us at Rogue 6/Ranger 12...if you want more Feats you could put in some Fighter, or maybe Monk...but let's just step up one level in each class, Rogue 7 is d6+3 more Sneak Attack and Haste Boost III, and Ranger 13 is the next tier of Favored Damage.
Oh yeah, and Human, for +Int, but also because HV is the only racial way to improve your Repeater damage.
Human
Rogue 7/Ranger 13
Str 10 (+6 Item, +2 Tome, +2 Ram's = 20)
Dex 15 (+6 Item, +2 Tome, +3 Ranger, +1 Human, +1 Exc = 28)
Con 14
Int 18 (+6 Item, +2 Tome, +5 Levels, +1 Human, +2 Exc = 34)
Wis 8
Cha 8
That's right max Int...what the hell...
So many skill points...leveling order doesn't matter TOO much...just end on Rogue at 20 to finish off a bunch of skills.
Granted Feats: Bow Strength, Rapid Shot, Die Hard, TWF, ITWF, GTWF, Manyshot, PS, IPS, EWP: Light Repeating Crossbow
Chosen Feats: Point Blank Shot, Rapid Reload, WF: Ranged, EWP: Heavy Repeating Crossbow, IC: Ranged, Toughness -- Two Feats Leftover
Basic Attack
------------
18 BaB
9 Dex
5 Weapon
1 Weapon Focus
---
33 (+2 vs FE x 3, +2 Sneak Attack, +4 Sniper Shot)
Add other modifiers as they are available to you.
Basic Damage
-------------
9 GS Heavy Repeating Crossbow
12 Int modifier
5 Weapon
2 Ram's Might
4 Greater Heroism
---
32 (+10 vs FE x 3, +23 Sneak Attack, +5 Human Versatility, +1 Threat/+1 Multiplier Sniper Shot)
Add other modifiers as they are available to you.
Might want to pick up some Midnight Greetings to use with that Int too.
An excessively amusing array of skills.
Excessively capable Disable Device and Search ability.
Good long-distance ranged damage with a high rate-of-fire, significant point-blank Sneak Attack/Favored Enemy damage.
Since Turbine killed my Repeater Ranger at Level 10 (that's when Arcane Archer got taken away from him) he'll be transmuted over to this to give it a try. I probably wouldn't try and level up this way. Would start with a high Strength and just smash my way up a few levels then LR over to this later.
Depending on the usefulness of traps, and Deepwood Sniper II, the class balance could be shuffled around.
What the hell.