As maddening as this may be, "Mom friend Miku-imitating" Yuri has some good points (at least by this world's standards). They already know that it's not going to end with him just choosing one. So it's best to establish an hierarchy first with Miku and Yuri standing atop as equals, and the rest could be friends with benefits and/or concubines.
Of course, I don't expect it to go that route. Too many obstac... rivals...