I'm in the process of helping a friend set up a system with a 185 softie display, a 55 display fuge underneath, and a common sump located remotely in the room adjacent. It's too new to really comment on how well it works, but we plumbed each tank independently with its own pump and returns. It's filled and works like we expected. You can shut off either (or both) tank(s) and the water stays off the floor. Be sure the sump is large enough to accommodate drainback from all tanks simultaneously in the event of a power failure.

Two sumps would give me a headache personally. Put them at the same height and run a balance pipe between them so they stay at the same level and it *should* work out. I still think I'd find a single big(ish) sump. It's the same reason multiple carburetors suck, lol. On paper its great, in the garage it's a hassle. In a giant interconnected system you don't need more volume, per se. Just a box to wrap around the ugly bits.