Well the question is "what if"(I think that's what he asked), so let's just pretend ZUN did decide to sell it, or collaborated with some big-shot company.
For me it'd either be IF or NIS. 'Cause honestly speaking, I doubt any western companies would take it. So that leaves JP devs to take the franchise. Companies like SE is too busy milking their main franchise, to handle another series.
So it'll have to be the next best companies that actually goes for a lot of Moe, and animu. Which is ofc, IF or NIS. Nintendo is a possibility, also ones such as Bandai Namco, Capcom, etc.,but I srz think IF or NIS would be better.
There's a lot of ways how they'll remake the series. So I don't really know how. But if you played their games, they'd probably do some similar things with the franchise. Plus, add more Moe and ecchi.