Your Replusor and Sawblade combo has been done on a pair of Cotton Alley levels.
As for blades and portals, that would be a good idea, but you'd have to check the editor to see if they interact. The game does use fireballs and portals in a few places though.
I don't mean like that. I mean the small saws that are shot from saw shooters, bouncing on the repulsor.
The fireballs are affected by gravity, so the can't shoot straight forwards, tho.