A basic shorty wetsuit will fine for most spring/summer/autumn days provided you have good spray top & trousers to wear over it when the breeze/spray is up. I can't emphasise enough the importance of that outer layer - on a cat trampoline you are exposed to the chill of wind and spray from head to toe, unlike many dinghies where the hull gives some protection to your lower half. On the sprint 15 we have the luxury of the 'cocktail cabinets' (centre hatches) which are perfect to stuff spray gear into on hot days in case you get cold later and need to 'layer up' out on the water. A warm hat is another cheap but effective addition - also easily stored in the cocktail cabinet.
My personal outfit is a mash up of bits purchased over time. I've no particular brand affiliation. I normally weigh up price/features/special offers whenever I'm in the market to replace a particular item. I don't have any Zhik gear at the moment, but if I was in the mood to treat myself to something extra nice that is where I would look first.
Hot & Calm Days:
Wetsuit ankle boots (Decathlon - cheapish but pretty good and comfortable hiking with toe straps)
3mm neoprene shorts (Palm)
Cheap oversized swim shorts (over the neoprene shorts to protect them from wear/damage on deck fittings)
Rash top (long or short sleeve. various makes. Widely available on Amazon and Ebay as well as watersport retailers)
Colder/Windier - I add ...
Spray Top (Gill)
Spray Trousers (Crewsaver)
Colder/Windier still - I add ...
3mm Neoprene Long Sleave Top (Gul - under spray gear over rash vest)
Feezin' - out with the above, in with...
Wooly Bear (underfleece suit)
Drysuit (Gul)
Cheap oversized 3/4 length lightweight tracksuit trousers (over drysuit to protect seat/knees from wear/damage)
Mountain hat (waterproof fleece-lined peaked hat with ear flaps - feels as warm as it looks daft!)
Nice thing about the drysuit is you can add more layers inside the colder if gets - provided you stick to synthetic materials (e.g. fleece tops) that won't absorb moisture.
Long john probably better than shorts if you like the extra knee protection. Also my shorts are only waist-height without braces so can slip down a little when hiking - a long john wouldn't have that problem.
As a mainly unarig sailor I haven't bought a new trapeze harness in years - designs and comfort have moved on a lot since then. I'm not sure what to recommend.
I wouldn't recommend a Mankini - certainly not under a trapeze harness