dont get ottos...this is why i am having to get rid of my discus. every time i look into the tank i see her being harassed by an oto stuck to her forehead or her side.
i have kept clown plecos and BNs with discus perfectly fine, and of course corys work good too.
i would personally just recommend no otos with discus.
but then again plecos and otos have the same chance of eating the slime coat.
and i would stick with 5 discus, then maybe you could squeeze in a bottom feeder and a small tetra school 7-10 or less.
if you go with discus, do you plan on a planted tank?