In one of the few updates for the open source branch of Construct Classic before development on it pretty much died, the platform behavior got an interesting feature - being able to selectively toggle collisions with specific objects. For instance, holding up to walk up a set of stairs while moving towards them (while moving past if not holding up), or onto a lift (if the lift is moving up while the player is holding up, the lift will carry the player upwards, and will simply pass by if not).
Another interesting example includes changing to another 'layer' of the map - for example, going upstairs or downstairs in a top-down view without changing layouts, or entering a building that's in the 'background' with a sidescroller view. Such things can have some interesting possibilities for map design.
Stuff like this, though, isn't really feasible right now as things are - you could switch solids/jump-thrus on and off, but that will cause a myriad of problems for other things using those behaviors, especially if you want things to be still be active on multiple 'layers', for example.
So, yeah, for certain behaviors like Custom Movement, 8-Direction and Platform, I'd really like to be able to selectively toggle collisions with specific objects.