People need to get real about what's actually got a chance of being on the undercard. Maidana v Khan could easily headline it's own card and do big numbers so why put them on a card where it will make naff all difference to the buy rate? Lomachenko and Walters would do OK numbers too, if that had a decent co feature, say, Golovkin v Heliland.
I think you could get away with underpaying the undercard boxers on this card, sell it as the biggest platform the boxing world has ever seen, the chance to become a legitimate household name. I would try to get Broner vs Maidana 2 for one.