The difficulty of doing this with the existing habitats is that they are separate and individually weighted. So if I connected them with rigid tubes, then tried to pick all of them up, they would shift relative to one another and crack the glue/plastic where the tubes pass through the habitat walls.
My solution to this is a partial return to the Mark 3 approach: One gigantic, single structure. To prevent stress on the tubes, all three enclosures are mounted rigidly to a metal platform that I'd need custom cut/milled for this purpose, with holes in the correct places for the screws, and some type of coating to prevent corrosion. The four ballast pods are attached to the bottom, as shown, for a total of eight 5 pound lead block weights, totaling 40 pounds. You can begin to see why I resist the pressure to build bigger and bigger habitats. This is about the absolute practical limit for a habitat intended for use in a fish tank. The Mark 3 was even heavier.
Anyway, this would be amazing to build and to witness in operation, but it's purely optional. The Mark IV (Hambase Alpha) is entirely sufficient in size for three hamsters, with submersions of one week at a time. This larger habitat would be tremendous overkill, and sufficient for deployments of many months at a time due to the dedicated rooms for food storage, and "waste", which would solve the only design concerns that limit the current model. You could leave the Mark V underwater pretty much as long as the food and water held out with no hygenic concerns and certainly none for the space available as it would at this point be far beyond what the animals actually need.
I will only build this if you want it, and I can only afford the parts if you fund it. This project would cost between $300 and $500 dollars in total. So far donations have been $5 here and there, with a very few generous $10 or $20 donations, and a single surprising $100 donation (many thanks, you know who you are). While deeply appreciated, this rate of donation won't support the construction of the Mark V. I have no way to rally all of you towards this funding goal as Kickstarter refuses to approve this project, so it all more or less hinges on whether any one specific reader decides to foot the entire bill, or most of it. If one of you does this, I can guarantee that the Mark V will get built, as proven by the long line of earlier habitats completed so far. It's all down to how badly you guys want to see a colony of this scale.