I'm actually just building one of these, even called it my Arcane Sniper as well. right now I have
Human, stats with 25 pt-buy 14 Str, 17 Dex, 12 Con, 15 Int (17 adj), 12 Wis, 7 Cha
Slayer (Sniper) 1-2
Exploiter Wizard 1
Slayer 3-6
Arcane Archer 1-3
Arcane Trickster 1-10
Spells at level:
3: 0th, 1st
10: 2nd
12: 3rd
14: 4th
16: 5th
18: 6th
20: 7th
Traits: Magical Knack, Reactionary
Feat at 1: Point-Blank Shot
Human Bonus Feat at 1: Precise Shot
Combat Style Feat at 2: Focused Shot
Feat at 3: Rapid Shot
Feat at 5: Experienced Sneak Attacker
Weapon Training at 5: Longbow
Feat at 7: Spell Focus (Evocation)
Combat Style Feat at 7: Improved Precise Shot? Clustered Shots?
Combat Trick at 7: Bullseye Shot
Feat at 9: Greater Spell Focus (Evocation)
Feat at 11: Selective Spell
Feat at 13: Maximize Spell
Feat at 15: Quicken Spell
Feat at 17: Spell Perfection (Fire Snake, Maximize)
Feat at 19: Clustered Shots?
Spells:
1: Vanish, True Strike, Gravity Bow, Burning Hands
2: Glitterdust, Sonic Scream, Selective Burning Hands, Invisibility
3: Lightning Bolt, Selective Sonic Scream
4: Greater Invisibility, Detonate, Selective Lightning Bolt
5: Quickened True Strike, Quickened Burning Hands, Fire Snake, Selective Detonate
6: Selective Fire Snake, Antimagic Field, Cold Ice Strike, Maximized Lightning Bolt, Selective Maximized Sonic Scream, Quickened Glitterdust
7: Delayed Blast Fireball, Selective Cold Ice Strike, Maximized Detonate, Selective Maximized Lightning Bolt
BAB suffers (caps at 14), as does hit die (avg 7.8), but has 8d6 sneak attack (plus Slayer level of 6 when sniping) and can cast up to 7th-level spells of the Wizard spell list.
It can use invisibility and glitterdust to get sneak attack damage, and with quickened spells/cold ice strike launch 2 imbued arrows per turn.
Havent played it yet but really want to