If anyone is curious, I found this worked best. All the stock maps are fine and several custom maps with this as an add-on worked.

_callbackglobal::SetupCallbacks()

I'm writing a mod to essentially make any map have a buyable ending. I have everything in a few custom named gsc files, but buyable_ending.gsc contains all the calls to the other code. I want to insert

map\buyable_ending::init()

Into any map (hopefully) regardl...