Hi Walther! You know what we like already. Just keep doing what you do. I appreciate the modular design of your trucks and this has let me make all sorts of custom rigs such as an international bucket truck and a GMC MoW equipment for my Conrail layout.
I think that some construction vehicles would be nice. We were in dire need of passenger vehicles a few years ago, but this head been largely addressed with Shapeways, where small vehicles are detailed and cost effective enough to be practical. The same can not be said for trucks and construction equipment. Both feature parts far too fragile for handling. These need to be pewter.
A backhoe - Case or Deere would be great. Even better with an etched enclosed cab. These were standard equipment, carried on trailers like yours behind MoW trucks that you currently have available. I would also jump on plow and snow removal equipment. (for that matter what about lawn mowers and snow blowers as an accessory pack for your landscape trailer?).
Really I do buy anything you make. It's just that good. Though I love stuff for my era - 80's and 90's, I enjoy the older stuff too.
PS: I have not forgot about the RTS bus. I still need to get to Maine to photograph it.