A steady customer base needs to be business traveller, ideally a route deal. For London to NY point to point in business class, it really needs to be the financial services industry. The big players won't trust a startup, so you need somewhere willing to take a little risk with travel in exchange for lower fares, but that is still sending people in business class. Tricky.

One approach could be to sell the seats as premium economy, as an awful lot of companies have moved to that from business. If the price point is similar to World Traveller Plus, that could be an angle.