is it wrong to...

Use 1/4-1/4 cables to go from MPC 1000 MAIN OUTS into my effects processor, and then 1/4-1/4 cables to go from effects processor to L/R inputs on my mixer?

mpc1000 main l/r outputs --->Peavey Kosmos V2 l/r inputs
Peavey Kosmos V2 ---> Channel 2 mixer l/r inputs

my mixer has gotten eq for each channel, so i was going to use the mixer for eq, and the kosmos for effects

thats actually a good way to set that up

My only advice is use balanced cables. When I first started setting up and routing my gear if I had know how important it was to have balanced cables it would have saved me some money and headache. Unbalanced cables can introduce unwanted noise and cause all kinds of nasty interference.

like ArKyve said, thats a good way of hooking it up, if your going stereo or main outs like you said. i havent seen that mixer of yours, but i know the mpc 1000 has 4 extra outs, so you may be able to do some extra routing for more tracks if you get the right cables.

but for what your trying to do, yeah that should be just fine. just use balanced cables whenever possible

are you using a dj mixer? or a studio mixer?
if your mixer has aux/sends or inserts, you should use those.