Well, I dont think normalizing module size is a good idea. You can have a tiny curve "cheese slice" sector as a module, a long straight piece, or an entire station, as long as they could be coupled together. In TT, we have this kind of norm
http://www.fktt-module.de/de/node/73where there are a few head piece variants standartized, both in track arrangement and in screw holes to keep it all together. Each module should have at least one, but maybe more of them, and can have any kind of form as desired (flextrack makes it possible). Small errors in arranging the rails are easily compensated when you first connect the module rails (isolated), and then the modules are screwed together.
Some of the modules in TT
https://www.tt-club-bayern.de/%C3%BCber ... ub-module/