Treaties are not moddable. Wait til SE5 where you can customize them in-game.
You can't mod resupply to cost resources. However, ship maintenance can largely be seen as fuel (and other supply) costs. Why else would you have to pay the entire cost of the ship every 4 months if it weren't fuel? It is abstracted, but that's ok IMO.
A lot of mods make other resources important too. Try Pirates and Nomads for the mod with balanced resource costs that is closest to stock. Other mods like Adamant, Carrier Battles and Proportions have more sensible use of resources as well, but are very gameplay-altering in many other regards.