Hi,
Please could you explain what it is you would like Jack to do/wear?
It is very easy as a gay guy to carp from the sidelines, demanding arse, cock, erections and cum, all available content anywhere on the t'intereweb. There's much I'd love Jack to do (and to let me do) but my fantasy is not Jack's reality! I'd much rather see Jack in tight CKs than a naked Tom Daley prostituting himself about for attention.
Jack is attractive, boyish, cheeky, desirable, engaging, fun, gorgeous, happy... partnered, straight, sponsored, with a career as an Olympian diver. I guess he is prepared to showcase himself in pants, or contracted via his management to approved and commercial publications, and we must respect his boundaries.
As for other underwear, why would he buy items to wear only for the pleasure of a gay guy? Jockstraps are not as popular in the UK; Andrew Christian are very much a personal choice; Armani, Aussie Bums, Boss, Gucci, RL, Versace, etc are no different to CKs in design and look. Although I agree on PUMP! and some 2(x)ist would be good!
Anyway, Jack, I'm very happy seeing you in your underwear!