I think you need a minimum of 7 strength for most assault rifles (but not all?) and high perception, so a mixed psi/AR could work, since you can dump dexterity, unlike with pistols. Thought control with a splash of psychokinesis is probably best; even with 10 will a combination locus of control followed by an offensive ability like bilocation is nasty. The only real downside I can see is that with both low dexterity and agility, your character would loose initiative rolls most of the time. And with the psi hit point penalty, I'd suggest not lowering your constitution too low.
Maybe something like this?
strength 7 (add 1-2 points to get 8-9 and wear the best armor)
both dexterity and agility at 3 (oh well)
constitution 5
perception 8 (add 2, not sure abut what perception feats ARs use)
will 8 (add 2 for locus of control, but this can wait, because you also need high thought control)
6 intelligence (for premeditation)
If you leave your strength at 8, you can add 1 point to intelligence and get some crafting feats, which is probably better. I don't know how well the heavy armors compare, but my mage managed just fine with a tactical vest and a crafted shield. The only notable exception were enemy snipers, because they seemed to have infinite range (e.g. she would get shot by an enemy outside of her sight range).
Keep in mind that I've never tried a guns character, so I might get some things wrong.
edit: I also had a look at the possible AR feats and wiki indicates you need 7 strength for full-auto.