Well, editing with the game has one thing the map editor will never have:

Collaborative map editing.

The map editor is just to show you what is coming up.

Ben said he would share the source of the Map editor so he can work with the game and let another developer use the source to make the map editor better....

We have now the map editor, but it mostly suck...

But editing in-game actually kinda work (even if slow).

Since now we can save in-game maps, editing with the game is feasible.

But, the normal gameplay constraints are problematic... Someone know a way to mod or hack the game to have infinite blocks at least? Or how at least disable the server hack detection, so you can do whatever you want in your own server?

Also, can I suggest as features, the ones needed to map edit from within the game?