Sounds like a real neat dio in the making. The Renwalls do leave a lot to be desired...but I have found that they do offer some "usable/pasable" parts for a scratchbuild...and for inspiration...at least for a vehicle that is implied/plausible...but not 100% accurate to a prototype. The neat thing about building vehicles from this period, is that there is such a huge selection to choose from for inspiration/ideas. There seemed to be a 100 or so auto/truck mfrs around this period....and thats not to mention all the cobbled together stuff I have seen in photos.
I also have an old 1/48 plane kit stashed away....its a Fokker.....I was thinking of doing some kind of WWI water-front hangar scene for a float plane, that was serviced by a small 60cm ga. RR. (once saw one like this by someone else, and it really just got under my skin).
The Lindbergh kit I have is the "Fireboat"....I was always hoping to someday convert the hull into a 1/48 scale "African Queen" type of steamer.
....and ...like you said....so many more one dreams of someday building.