I would like to be able to have betterx mods enabled while keeping a skyblock world on, but to do this properly you have to be able to use the betterx world type. Ideally, you would be able to specify a world type for all non-void worlds in the config.

Do you mean by "betterx" mods are mods like BetterEnd and BetterNether? It supposed to do it automatically, but I'll see what I can do... been busy lately with IRL stuff so it probably gonna took awhile.