[quote="Sprung"]@Rafalpluk has been exploring this for a slightly different mod and made a bunch of github tickets for where he struggled. IIRC his discovery was that it's generally easy, but in areas where gameside support is missing you might need to copy-paste a gadget and change a hardcoded unit list to contain your duplicates.[/quote]
Yes, as Sprung said. Copying units, weapons and features is easy, and they work. The problem is hardcoded units names in gadgets, widgets and AI. I fixed almost all cases in gadgets, but a lot was left to do in widgets, and then run out of mana to continue my mod.