We wanted our doors round too, a hobbit hole door.
We made concessions for the reasons folks have mentioned.
We gave the door one straight edge for hinges. And we straightened out the curve near the bottom so it was more like a square door entry, not so much of the door frame curve blocking the entry. Even still we notice that the botom curve blocks loading a big cooler. The comment about door weight are important -our homemade doors ended up much heavier than standard mas produced RV doors.
Ours look like this. It's as round as we could manage to build.