Probably possible to do constructor frigates, whether thats going to be doable for a different type of unit... Dunno.

I doubt it... but you might be able to "fudge" it somehow. I really don't know enough to judge.

Well currently even though we can now edit the binaries i have had only limited success, my first test was getting planets to spawn heavy frigates instead of constructors,(via swapping their frigate role types), unfortunately whilst this works it breaks both the unit ai and build menus (The construction frigates no longer auto-build structures and can leave gravwells, and the build menus are on the heavy frigate and they cant leave gravwells). Logically this proves that Unit AI is obviously done via role types (which is something else entirely), but additionaly it means that the role types are listed and have additional modifiers attached to them somewhere.

Where is my question?

Because im assuming that would also be where one would add new roletypes, which would seem an essential part of modding

2nd attempt test was trying (granted i didnt expect it to work) to change the "maxModuleConstructor" line in the planet entities, to "maxFrigateHeavy" in the hope that it was a variable based on unit roles rather than something hard-coded, but no joy. Unshockingly.

the thing bothering me most is that i cant find What makes planets spawn constructors, the planet entities contain the upper limits for them but not the spawn command.
I imagine its probably a function of a "colonised planet" over just a "planet" because neutral planets dont spawn them, but i cant find anything that distinguishes the two.