Not a dumb question, I've wondered the same thing. Unfortunately, I don't have an answer.

Maybe call a trailer shop and see what they say. 

There is a member here, River Dad, that builds/refurbishes trailers, ROKE custom trailers. Maybe send him a PM.

Biggest problem with powder coat is that is does not like standard bondo.   They do make a powder coat friendly body filler,  but it costs a bit and is harder to work with.   We are getting ready to do a PC trailer for a CP and we are leaving all the welds exposed,  so we will see how it turns out....

RD