Skimmer won't fit on my tank

I have a 200ltr fluval Roma, and a 20-30ltr spare tank. I want to put my skimmer and heater in there, mainly because I can't fit my skimmer on my tank and aesthetic pleasure.

I don't thnk this would be a sump or refugium as I have no DIY skills to make separate areas etc but I wanted to know ...
1)What people think about this- other than looking neater on my DT and slightly more water in total can it bring other benefits?
2)What this would be called? Other than tank under a tank, it wouldn't be a refugium so does it have it's own name?
3)What do I need to do to ensure if the power goes off nothing overflows?

I'm trying to keep things easy for set up, the stand is divided and if I take the divider away I would then need to reinforce the stand etc and I don't trust myself to do an adequate job any way through that process. I know my strengths and DIY is not really one of them. I did think at one point I could add another small tank and connect all three?

Any help much appreciated!