my last playthrough was a psi crossbow build since i dislike traps and absolutely love thought control so here are my thoughts on it.
to be honest, i passed the whole underrail using mk1 shock and incendiary bolts. started using my ridiculous stash of several hundred mk2 and mk3 bolts only in dc. also most of the time i used monsoon crossbows since they have the best looking art (yeah, really a good reason).
anatomically aware scope is a must have upgrade and i used pneumatic reloader more since super string boosts only mechanical damage.
build:
st 3
dx 5
ag 6
cn 3
pe 10
wi 8
in 5
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crossbow 15
evasion 15
dodge 15
stealth 15
hacking 15
lockpicking 15
chemistry 15
though control 15
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aimed shot
marksman
sprint
concussive shots
ambush
opportunist
special tactics
elemental bolts
sharpshooter
critical power
premeditation
locus of control
skinner
power management
the feats are approximately in the correct order. i put points into will to get locus of control and intelligence for crafting feats. if i remember correctly i didn't raise perception above 10 and the last 2 points went into agility. chemistry was the first crafting skill to get to 20 and mechanics to 10 for incendiary bolts (i think the metathermics guy at sgs sells the blueprints) and then later electronics (the blueprint was in gms but don't know if it's random loot or not).
now that i read Wildan's post, blitz seems like a good idea but i managed without it. i also second his opinion on infused siphoner leather stuff because it's great.