Skyblock is confirmed and is coming
Freebuild is dead. Creative was a horrible attempt to capitalise on the popularity of Skywars and Eggwars, because apparently the game could not have survived on its own without a spark of Cubecraft "originality". The fact that it wasn't shipped with World-edit, despite many requests for it to have been, suggests that they just didn't care. This is of course reinforced by the fact that Factions required the removal of one command to be playable, yet when a friend of mine asked somebody to remove said command, he threatened to remove the entire game. We were told that Skyblock and Factions would be returning in early 2015... and then in summer 2015... then "definitely by the end of (2015)"... and then "early 2016", followed by "early summer (2016)", led by the end of summer 2016, to... "confirmed and is coming". It has been over a year since Creative and almost three years since the original announcement.
The suggestion
Nobody wants a masterpiece, they just want something that isn't "Skywars with a twist" that they can do on their favourite server, something that involves the community. I was once told that the management team holds on to every build, every map that has ever been on the server. No doubt this includes the two Skyblock spawns. The Skyblock plugin is free and public, and is also reliable.
Just add Skyblock to the server in its imperfect, vanilla way, just like it used to be. Put the old spawn onto a map, add the plugin, and put it on the server. It wouldn't take very long at all to give us what has been promised for almost three years, and nobody would complain. Nobody would complain, because nobody ever asked for anything spectacular, they just want to be able to play their favourite game without having to go to a different, more than likely pay-to-win server to do so.
You can introduce pets and cosmetic overrides as micro-transactions, or even more player slots for islands. Just please add Skyblock like you said you would in early 2015. Slap the 'beta' label on it, assign a couple of Sr. Mods to be Admins with permissions to edit the world, and voila: Freebuild is back.
If for whatever reason the maps aren't there anymore, then I'm sure players wouldn't mind using the old Skywars lobby for Skyblock.
It's so insulting that some of us have waited for this game for over two years, yet instead we get "Eggwars but with two eggs, and if they both break you lose. Also, you can't criticise it because it's a beta even though we never specified that before hyping the hell out of it".
In regards to lag, you could use the Assassins / Creative system if it's that big a concern, add multiple servers (i.e. a vanilla version, an OP version, and a version with McMMO), or do what Saradabaschi did and allow up to eleven people to occupy one island.
tl;dr - Add Skyblock