I feel adding a survival world (SMP) into the CubeCraft's networks is quite unncessary and has been suggested a couple times on the forums before and hasn't gained any love for the idea. An SMP wouldn't fit into CubeCraft's current gamemodes either.
It's pretty easy to create an SMP for singlemode or multiplayer if you wanted to create one. However, I personally think adding an SMP to CubeCraft would only make it a case of P2W (pay to win) and wouldn't be that popular after the hype of the game's release <3