I think the trick would be to make it look like there is one big enclosure but to actually have them separate. Fish tank at the bottom, terrestrial landscape for the turtle and an arboreal enclosure above. All decorated with one theme and something fancy to make the dividers look natural. It would be much better/easier with access to the back as well. Just a thought.
If there is anything the nonconformist hates worse than a conformist, it's another nonconformist who doesn't conform to the prevailing standard of nonconformity.