I know this is going to sound like a lame answer, but as a fellow male i can't really say to you what i think you should do as what you like may not be what i like and vice versa. That's part of the joy of WAM and fetishes in general. Everyone is different. My suggestion is do what you like, don't go too out there yet, establish yourself as a brand first. Let your imagination be your guide.
I've noticed what guys are into here is really niche so what appeals to multiple guys is going to be themes.
I don't have any specific interest in singlets but a good mankini if it's degrading is hot. By itself it's not special. A guy being stripped and dressed in a mankini in front of friends or partners would be super hot.
Suit play can be hot but it depends on the guys involved. A bad suit isn't hot. A suit by itself isn't necessarily hot
Long way to warn you that male wam isn't super profitable. You can make excellent stuff people remember forever but it won't sell dramatically more than the shit of the week.
Most guys do low effort, poor camera quality, bad lighting and color contrast, minimal mess.
I won't waste money on it but if people recoup the costs for their luxury goon sesh they're often fine.
Sorry to sound cynical or dismissive. Do what you wanna do!