Wile E Coyote
Out in the streets, they call it murder!
Can you run the rhino lining, or whatever you decide to use, along the body over these rust bumps and help prevent them from spreading? Would you have to get up under the wheelwell to prevent moisture from continually getting up behind the paint?
Any bedliner-like coating would flake off, with a quickness, if put over that bubbling. Rustbullet, POR, Zerorust, etc would last only a little longer. Any top coat relies on the adhesion of each preceeding base coat, so loose rust is out, even for quality coatings. Now, if ya were to get that area down to SOLID rust and/or bare metal, then we can talk.
Herc, Rhinolinings and the like aren't ideal choices for longterm solutions even on solid rusted areas. Better to use something intended to encapsulate the rust, then top coat as you wish if ya need to.
As I've heard preached everywhere, the PREP work is what makes or breaks any paint job.