I'm actually trying a 5 different class setup as well. I have the standard 5x Shammy team that I screw around with, but my actual PVE team I'm leveling (which only hit level 10 last night though, btw) is the following:

Protection Paladin Tank
Disc/Holy Priest (Swappable with my Restoration Shaman on my 5x Shammy team since they are on the same account, I love Resto Shammys)
Boomkin Druid
Frost Mage
BM Hunter

It's kind of a crazy setup doing 5 different classes, but since they are all casters/ranged, you can still just map similar abilities together. You might lose some efficiency though since its less likely that the cast times will be on the same page. It's throwing in melee that really puts a wrench in the whole thing.

I intend to refine my macros and such along the way, but I think it's doable.