Well, i just had some ideas i'd like to see in Mari0 SE:
The first one it the pipe entity
, that mixes the regular pipe entity with the warp pipe, so it's easier to use, also i think using IDs would be a cool idea because you could be able to put more than one pipe connection between two sub-levels. (the "in level" part is so the game has less IDs to search to find the correct one (i guess it works like that :P)
The second one is the pipe end
(receptor/however you want to call it), with directions, IDs to receive it from a pipe entity, not much to explain here.
The third one is the door entity (it should be in game), so you can use up key to go throught it, same as the pipe entity, ID's (no directions for obvious reasons), "in level" option to prevent to much load (i guess) and since in SMW there is a door that only small Mario can use, i thought about adding that as an option.
Fourth entity is the end door
(receptor etc...), this explains by itself after the previous explanations.
Fifth one is the conveyor belt entity
, which is pretty much what SJB wanted, you can set the spedd and the direction of it, and link the default direction and state (ON/OFF).
Sixth one is the wind/water flow/presure entity
, which can be used as a drain, wind, low gravity zone, which ever you want (if Maurice adds it, of course), it should have its respective Wind end entity
which should have an option to stop it horizontaly and/or vertically.