Hey Again, welcome to the forum.
I hail from Foster (originally) so, lovely to see another Gippslandian joining the fold..... oh, that makes it sound cult-y, I shouldn't give away the addictive nature of Betta keeping just yet.
As for the multiple bettakeeping conundrum, well, I think we all have our own ways of getting around it..... do a search for Shadoh's fish room tour to start with.
For us cool climate southerners, a barracks system is a good idea - and a nightmare to design.
You could always partition a large tank, work out a way to heat and filter the bloody thing, and you're half way there.
I'm working on a barracks design for 8+ fish at the mo'..... I'll keep you posted on that.
The mirror box looks good size-wize, but I imagine would be a pain in the bottom to photograph through, and the mirrored back might be a constant antagonist for your firey little steed.
it sounds revolting, but Kmart & Woolworths have a few really cheap ranges of straight-forward little tanks with filters/lights/etc all buit - in (just add water, and a fish..... and a heater...... and condition the water properly)
For a fraction of the cost.... not a bad way to see if you like keeping fish in small quarters (as opposed to equally small quarters, in a bigger tank, with more and more and m... oh)
Welcome. We like photos. Please take them.
-Ness