Sage international made a version of their EBR chassis for the mini-14. They are expensive, but supposedly help as much as the pin bedding job that Accuracy Systems does.
A trigger job can't hurt. And an accustrut may help some, but from what I remember they don't help the 582s as much as earlier guns.
But as everyone else has said, you can only improve a Mini so much.
A while back I picked up an older Ranch rifle that had the full accurizing treatment done by ARS in Texas (out of business now). It has a heavy Lothar-Walther barrel, had the gas system modified to clear the heavier barrel profile, a nice light trigger, and is glass bedded into a Bell & Carlson synthetic stock. It'll shoot 1.5" groups at 100 off of sand bags, and while that's impressive for a mini, it's really nothing to brag about for a gun that's had that much work done to it.