One of the big issues we have had with using a steel door with wood frame on our job shacks is water damage. Unlike a conventional building, there are no overhangs to provide any protection to the door. with an out swing door, the door panel is mounted flush with the outside face of the frame. Water runs down the side of the trailer and gets into the gap at the top of the door. It does not take long for it to start working its way into the top of the door slab. Depending on the brand and construction of the door it causes the wood interior frame to swell which results in the door sticking. Many of the doors are not galvanized so they start to rust along the top and bottom. A lot of this can be prevented by installing a drip cap/gutter above the door, and installing a flush door cap on the door slab itself which will keep the water out of the door blank. Pemko makes these, and they should be available from a local commercial door store for a few bucks. On our mobile office buildings where we want a standard door we are using a galvanized metal door from Curries, that does not contain any wood, all the interior braces and framing are 22ga steel.
The Mobile home doors are defiantly a lighter construction, but most of them seem to hold up fairly well even on trailers at job sites. If you are worried about someone removing the door you can always use security screws similar to what they use in restroom stalls.
Defiantly not trying to send you off in search of a different door, just wanted to let you know what my experiences have been. When the planets finally line up and I can actually start on my conversion, I will be using a RV entry door, mainly because of the flush latch, and built in screen. and the modern ones seem to hold up to the elements well.
I like your idea for a retractable screen, I had been looking at those for my house.