Thomas Eastside, Esq.
Re: Can I upgrade an upgrade?
Interesting question, but after looking at the rulebook, I don't think it is allowed. The rulebook explicitly refers to "upgrades" as trading cards. In the section regarding trading cards (see page 7), it states:
"Each blue trading card can displace any already placed building. Each red trading card can displace any already placed aristocrat."
Since the rules specifically don't include trading cards as building cards, I don't think you can "upgrade" an "upgrade".