At this point no it's not possible so far as I can tell because the metadata fields available for entry in Capture One are hard coded (you'll need to submit a feature request with Phase One via the support system) but typically the workflow I see with larger organizations that might need this type of metadata is that you shoot the job tethered to capture one, sync metadata (to create xmp sidecar files) and once the job is wrapped people will import the images into their larger DAM system - and honestly you'd be better off using existing IPTC standard metadata fields to avoid this specific issue.
That said, generally speaking I'd strongly recommend creating C1 sessions rather than using the catalog system they have going. It's advanced by leaps & bounds since it was launched but I personally still don't love it and prefer a different system.
If this custom metadata is a big deal for you, I'd definitely reach out to the guys at ShotFlow 1
http://shotflow1.com/ because their product sounds like it's right up your alley.
If you're doing a lot of high volume product photography, then Capture One is definitely the right tool (it's literally 700% faster for tethered shooing than lightroom as a quick example) so I'd give it some serious consideration.
Good luck!
