Lol I just Suggested a 2D player Type.... Reg said it was impossible
Wtf? That's possible. Just not easy.
Anywho, you should put all of the levels on one map, and connect the levels. Just use hollow pipes for the shortcuts, and people can use setPlayerTransform.
Also, to put a spin on things, slap barriers on both sides, and let us take on the world from a first person perspective. Might be a bit odd playing a first person 2-D game.