I'm definitely open to feature requests! :) And I will definitely consider all of these. As always, the biggest deciding factor of any feature will be if it can be implemented in a way where the outcomes are as unambiguous as possible. That might be tough with a couple of these, but we'll see!
However, there are a couple of already-planned actions that I think might help accomplish some of this functionality. The first is an Action that lets you change the sprites of a Thing (or the Player too, but that's a separate Action). The second is the ability to toggle on or off whether a Thing blocks the player. With those two in combo, with a Thing that looks like a Block, you could change the Thing's sprites to an invisible sprite, then make it not block the player anymore.
But thank you for the feedback! Like I said, I will keep them noted so I can mull over how to accomplish them in a clean, unambiguous way.