I have used it (rustoleum ) on smaller parts like brackets , braces , and such , and sprayed PPG's DBU or DBC BC/CC system over it and they have weathered well .
Did it to a Jeep roll bar and it still looks good !

I would think if you used a good substrate like DPLF ( or something comparable by another brand ) , over the rustoleum after all repairs are done , and then use a compatible primer for sanding repairs smooth , to accept a compatible top coat system , all would be good .

Just apply enough rustoleum to coat the bare metal , 1-2 coats max , dont need to just load it up , all you would need is just enough to cover the raw metal to keep it from rusting so you can handle it for repairs