Hmm Maybe build a shelving unit rack thingy lol basically where you can place your tanks on top of each other, but place the tanks on their sides so the opening easy to get at, Find some plexi-glass or old windows an make top hinged doors with a secure latch on the bottom! and as far as heat, you could make the selves wide enough to put lamps on the side shining in a corner, or under tank pads.

Just what I would probably do in your case, Cheapest thing that would work n use what you got.
Oh and you could put those eyelet thingys on the outside of the doors with a simple clip on the adjacent support Just to hold it open when so desired.