You need to find and modify where the spawnData field is used in the rest of the code.
Also, if everyone seems to be recreating e.g. the spawns from CityRP, the money system from CityRP, the hunger system from CityRP, aren't we just going to end up with CityRP again except now in twenty incompatible mods?
You should just make it so normal players placing a Spawn Point brick (the normal one) spawn there as a personal one and ones belonging to Super Admins or the city or whatever (e.g. unowned property like banks) are used for players without a spawn yet.