I really doubt that anyone would have a problem with you adding more spawn points. I am pretty much 100% sure that none of the custom mappers would do it. They have no copyright on their maps and earn no money from them. We just want our maps to be more popular. I would be honoured if somebody fixed up my maps
Editing commercial content however might have a slight risk. But again, I highly doubt it. Think of that Valve has allowed us to edit the entire game and make mods as long as you don't earn money on them. Then why should have anything against editing the entity list in a single map?
Sorry to say it, but this seems a little silly to me.