As others have said I doubt your consumers will mind whether it's GOS, Large Black, Saddleback etc once they taste it - I reckon a LOT of people wouldn't/couldn't tell the difference.
I had a friend up today whom I haven't seen for a long time, took her up to see the KK weaners and the first thing she said was "wow, I've never seen a black pig before" now she lives in a country village, surrounded by fields and I would've thought she'd have been aware of the differences in pig breeds - obviously not

Don't worry that one breed will be 'most popular' because ANY outdoor grown, traditionally reared pork will be much tastier than even the best the supermarket has to offer.
On the subject of breed names on selling, it's my understanding that unless they've been birth notified to the BPA (as breed x, y or z from registered pedigree stock) you can't sell it as x, y or z - it's got to be given another name like 'outdoor reared' 'traditionally reared' etc without mentioning a specific breed.
HTH
Karen x