I would recreate the Gravitron with nothing but sawblade launchers, some moving platforms that would periodically block certain saws so that the saws launched create a pattern for you to dodge. Can you survive for 60 seconds!?
You could probably pull it off with two rows of fans.
But it's not the same because gravity's direction isn't forced into changing :<
The direction of gravity would only affect the orientation of the character unless those moving platforms are horizontal. We'd still volley between the lines and if you get the numbers and placement right it can feel just like the original Gravitron! Besides, why should it not feeling the same stop you from making the level? It would still be fun. :-\
I still want to make a level, it's just that the current idea I have isn't exactly possible with what we have at our disposal at this juncture. Until a mechanic is introduced to allow us to do that, I must shelve this idea unless I want to butcher it together using other mechanics or I must find a new idea to pursue.
Also, I'm not exactly fanatical about fans.