I may or may not depending on my dads idea, I would move my female bettas into the 55 gallon comunity I have now and move my community fish to this larger one. I really want to try. I guess we'll have to wait and see.I agree, most fish prefer a wider than taller tank unless you have fish like angels (then taller is better).
If your looking to have bigger fish, make sure the width of the tank is atleast twice the full grown adult size of that fish so it has plenty of room to turn around. If you end up building this, make sure you post plenty of pics