I like your idea for a bio-tower above the tank..
The library here has a 1200g tank two sumps (50g each) with Mech & Bio, then 2 (eheims i think) in line after the sumps.. not sure the size of the canisters, but the canister pumps are the return pumps..
There is an overflow on each end, and power heads to limit dead spots....
The team that (used to) care for it did a great job, services it weekly did about 400g/week WC.. The new service company.. not so good. It is amazing how much better a tank does when people who care tend to it...
Good luck with this project, hope work (paid) picks up soon....