That's a stunning selection of fish. I've had all of these species, albeit not in the same tank.
None of them are strictly surface dwellers, although Mollies will prefer to feed from the surface. It's good to have bottom dwellers as janitors though, and some will also help with algae. I've kept Bristlenose Pleco's (Ancistrus sp.) with all of the mentioned species and they do well together.
Gracilis are smaller and more docile than your other selections but they should do fine if lots of cover is provided. You'll want lots of cover anyway to reduce fry predation.
The optimum dietary requirements are different, but not different enough that it couldn't be managed with a varied, high quality diet.
The biggest problem I foresee is population control because they'll overstock a 55g in a few months flat if you let them. Of course, you can always get another aquarium .
Several of our members breed all of these species. Membership comes with a periodic 'Trader' publication in which you'll find fish for sale or trade.
I'm looking forward to seeing the set-up, good luck!