Why should the 3 railers have to rework their layout to accommodate the 2R/3R engines?
You have to rework your layout so that all of the engines you choose to run on it work. I had to re-wire the Ross #8 curved turnout because short-wheelbase 3-rail engines or those with only two pickup rollers closely spaced (Atlas SW's, early Lionel Geeps, early MTH Geeps, small Box Cabs, etc.) would stall at low speed and lose their ground connections.
At some point in time, you'll have to rework something on your infrastructure to support a new purchase, even if you don't come anywhere near a 3/2 locomotive.
Clem:
I think the diesels are wired differently from steam and use double-insulated wheelsets. Steam gets complicated because there are so many moving parts that may directly or indirectly contact the locomotive frame, even if you double-insulated the wheelsets.
