Future Automation do a number of sizes. My system is 1 miniserver, 3 extensions and a few small units. I've got the largest 5 rail cabinet and laid it out as per Loxone's advice and I've used most of it. I probably could have managed with 1 row fewer but the extra space makes layout easier and it the spaced from having a smaller cabinet wouldn't have been any benefit to me.
I'm not sure how a full metal door would work - will be interesting to see. Not least both the Loxone units and Power Supplys appear to rely on pasive cooling via the bits that stick out of the cabinet.
I have a completely separate 17th Amendment Consumer Unit as Loxone is only linked to a small number of lower powered circuits - the two lighting circuits and a 'services' circuit. The Loxone power supplys will be run from an external UPS so ultimately there will be a fuse in a plug.
The Consumer Unit is a 15 way with 12 ways used and it's pretty crowded in there. The Future Automation cabinet would have struggled to accommodate everything.