I like simple solutions. Also I will use a paint system until it fails one time, then find something better. I also avoid new products for a couple years, until the manufacturer works out the "early production problems". When I get a system that works for me every time, I will NOT change it unless it fails. (Yes... they do reformulate products to meet EPA standards and such... and it usually leads to problems. I will not use the latest "trick-of-the-week" system, when mine is working just fine.
I have used 2K primer only for about 20 years with zero failures. Sand the metal good, then metal prep 30-60 minutes before primer, and NEVER has adhesion problems. The only time I would consider epoxy first is if it will be left in primer and exposed to the weather. As far as wetsanding, I do it on every job, and then seal and paint. No problems with this in 20 years of full time work.
I know I am a dinosaur... but I guarantee my work for as long as they own the project. That takes confidence. I like Marhyde's Ultimate Primer.