@kevo_koma:
Other than the minks, which other groups has Momo formed an alliance with? When has he ever led? When has he ever fought?
In contrast, Hiyori has been in Wano for 20 years and survived as a truly adored person.
She knows the needs and wants of current Wano. She would be the perfect leader to get them ready to join the rest of the world.
That is, she is best suited to lead them into rebuilding their torn country. Establishing trading commodities that can be used to trade with the outside world. Getting rid of all the corrupt officials. Bringing the people together based on her experience as the top Geisha.
Momonosuke knows little to nothing about the plight of current Wano. He has no experience in dealing with people, politics or even economics.
If he became Shogun, he would simply be a figurehead at best and a complete incompetent at worst.
Momonosuke is currently considered the leader of the alliance forces. Oda has indicated this a few times, particularly when Momonosuke transmitted his voice for everyone through the Merry's.
That said, I think I see what you're getting at. Hiyori should be the shogun now because she knows more about Wano now, while Momo grows up outside Wano so that he's ready to take over once he's more mature. It's a reasonable idea in principle, but I really can't see Oda deciding to go this way for two reasons. First, he could have done the same thing with Vivi/Rebecca/Viola, since they are heirs to kingdoms with their rulers still alive… but Oda just wanted them to remain at home. Second, the Strawhats are all willing to put their lives on the line to help Luffy achieve his dream. Momonosuke has been single-minded about trying to save Wano and become it's shogun, so it's hard to believe he would turn his back on that to become a pirate.