The stand will be a little different than standard. Its going to be 6 inches wider than the tank, so the stand will extend 6 inches past the back of the tank. There will be 6 legs, 4 supporting the tank, and the other 2 supporting the extension piece. I'll be able to place the sump directly under the external plumbing.
The steel will be larger than 1". We are still working out the details on that.
T5's just for now. My last 120 gallon had great success using the old school ATI Powermodule with Reef Brite combo. I would like to go all LED eventually.
As for the return pumps, redundancy mainly. I like the idea if one happens to go out for whatever reason, my tank will still be circulating through the sump. They won't be run at the full speed / wattage. I've already got the M1s and am excited to play with them.