By the time most people know that they need a roof repair there is damage to the structure... rot, mold, etc.
I have never seen a painted on roof that lasts very long.... if it allows moisture to weep under voids, cracks, SCRATCHes the rot in the roof will be enough to doom the camper. When EDPM Oxidizes the surface washes away as a white milky looking mess... over time it all washes away and you'll be asking the same questions again.
TPO dosen't have seams... you can roll out a piece 60 foot long if you want.
Remember when the plastic dash boards in vehicles would crack as the pthlates (the chemical that has the new car smell) dried out.
TPO doesn't have pthlates and it doesn't oxidize.
Do it once and do it right. You have a $100,000 invested in your truck and TC if you bought them new.
Would you paint a thin coat of rubber on the roof of your house and expect it to last?