I used a dry suit a few years back when catamaran racing was my main watersport, but have not used it with the wayfarer (yet) so can only offer a few general comments.
Mine is a Gull which I think cost somewhere around £250-£300. It was ok to start off with but after around 3 seasons of average use started to leak. I had it pressure tested and was advised it was not worth having any part of it repaired plus the manufacturer wasn’t interested – so all in all pretty disappointing. I wouldn’t buy another Gull suit but I have no idea whether an alternative would be any better or worse.
Mine has a breathable upper and non-breathable lower. I’m a bit sceptical about breathable fabrics in general, probably a bit better than non-breathable but best not to expect too much from them. Once you are wrapped up in a bouyancy aid (+ trapeze harness for cat sailing) how well are they going to perform?
Zip – definitely front zip (well definitely for blokes at least …) also rear zip needs assistance to do up and undo.
Reinforcements – some form of seat reinforcement would be good, possibly knees as well.