Custom Power-Ups, Sheilds, etc.

I've done a lot of digging on this subject, and found very little... oddly enough. I was wondering how I could add custom power-ups and/or monitors to a wadfile. Is it possible to use the three actions for the S3&K monitors that were removed and replace them with new actions? I don't want to create any new abilities, IE: I don't want to add any abilities not already in the game, just new power-ups. Would I need to create an entire new exe file? Or is there another way around it? If it helps, specifically, the ideas I had in mind were:

-A temporary float power-up
-A permanent* bouncy power-up
-A permanent* jet-pack power-up (movement similar to spectating in multiplayer)

*Permanent similarly to the fire-flower or barriers

I had more ideas, but if I can figure these out, the rest should be simple enough. So how would I add these to my wadfile?

Mmph. Custom objects with these actions that set the player thing to a custom frame that allowed for these movement commands.

Or something like that.

Custom frames? As in sprites? I don't think that'd help much...

Where are actions defined at specifically, and how do I add custom actions? Just knowing that much could help out a lot!

No no no! I meant states, as in one state an object's in? A state with an action that would do what you want in the player's thing slot, and then another thing that would always jump to the player's position and have the sprite that you want, like a jetpack. Or make custom PLAY, TAIL, and KNUX sprites...

I'm pretty sure that adding completely new powerups into SRB2 is impossible without editing the source code. You should be able to get it to provide existing powerups in new ways, such as a fire flower monitor, but I'm pretty sure it's impossible to say, create your own shield.