Metering?
Put meters on the sub-feeds to each building.
I could see needing them, if one business goes out, and the other doesn't.
But that decision should be up to the customers, and how willing they are to trust.
I don't like your inspectors idea.
I can see why two TS's may be an issue though.... if one is paranoid that the two hydro services could somehow short to eachother.... but that would be a miracle.
Ups? personally, I wouldn't upsell those to my customers. I'd find a deal on two generators, if I had go that route. Probably cheaper anyway. Fancy things break easy.
Good luck