Dremels tend to melt plastic, more than cut it... They're too fast, and there's no real bit for "cutting plastic" made for them. You'd be further ahead with the Lexan Scissors and such. You can buy a plastic scriber at Lowes cheap (look where they sell acrylic, usually near screen door crap).
If you want to ball out, look up plastic cutting tools online... You can get some specialty stuff on ebay cheap sometimes.
I'm not sure what thicknesses you guys are dealing with but Lexan tends to be thin and VERY pliable (RC Car bodies), so scissors may not work on something super thick (1/8th or so).
Anyway, as noted above, Dremels MELT plastic more than actually cutting it. They're a little more tolerant on poly but when you get into (what I assume) is ABS, it melts quite easily. Thus it's ideal for vac-forming stuff, but Poly stuff you can heat and it'll retake its shape (SW figure limbs).
Not sure what these Anovos suits are made of. Dave, that would go for sanding too... Be light handed with it, and definitely you want one with a variable speed setting, not a cheaper one.
Paul, if you plan on donating that kit to charity, think of the children... IE: me.
I'd wear it driving around I think.
EDIT: BTW, Harbor Freight if you need "rare earth magnets" Matt... Also they sell nice riveting tools and tools that install snaps and stuff. Might be worth looking into. I hear that's the toughest part of putting together trooping armor (making it fit, and "stay").