I assume by Skyblock you are referring to where the whole world is defaulted to void space and then you have to manually expand it as you wish to build. If not please feel free to post images or explain what exactly you mean by Skyblock.

The main issue I see arising from a world like this is extreme griefing. If the world building area has to itself be made people are very likely to just take away the space of other players. Plus if the resources are restricted to being only in this "Skyblock" world what would we do about the limited resources? It would be almost on the verge of promoting stealing as so many items would be so rare.