This mod is lovely! There are times in which the player would prefer to spawn at world spawn instead. Thoughts on an approach similar to this (except it being a spawn near type option)?

(taken from https://www.curseforge.com/minecraft/mc-mods/herespawn)

As stated in the mod description. This is a server side mod.
Besides this, I wouldn't copy stuff from another mod. Just use that mod if you want that feature.