Do supply officers no longer build stuff in imperial levels? I now have to pay for imperial items and VIPs only make the construction time faster.
Correct- supply officers no longer start to build things in the Imperial levels. Instead, they finish off the project on that level that is already underway, no matter how much time is remaining.
To make the most use of them now, they should be delivered to an Imperial level where something is already underway with a lot of time left. The longest build times for Imperial items now are 1:50, much below the old 5+ hour ones for a few types.
They appear a bit different than the old ones (now having yellow helmets) as well.