If you are looking into more niches I think there are some big gaps in the VR market:
1) The biggest and most puzzling gap in the VR market is anal sex. I’d hesitate to call it a niche as it’s so commonplace in porn. I was absolutely stunned how few anal scenes are shot by VR sites. There’s countless sites purely dedicated to anal in 2d porn. Mike Adriano has three anal sites alone, you have Tushy.com, Tushy Raw.com. Evilangel are pretty much all anal, even a site like Brazzers, which most would class as vanilla porn, have multiple anal scenes per week. These are top sites too with top pornstars, lots of whom are shooting in VR but not anal for some reason. I mean someone like Emily Willis doesn’t even have one anal scene in VR and shoots nearly all anal everywhere else.
2) Interracial sex would be next. An absolutely huge market in 2d porn. I’d say it’s mostly black guys with white girls rather than black on black scenes. Not necessarily what I gravitate towards but a huge market.
3) Taboo stepfamily roleplay. This is literally everywhere in 2d porn and not hugely prevalent in VR yet.
4) The other gap would be on the more extreme side. I know you removed the piss scene so that is out but scenes with face fucking, gagging blowjobs, choking, face-slapping. There’s plenty of pornstars who love that stuff and guys who are into it.