Personal thoughts:
Sadly, I don't know Team M too well, but a few members that I think have realistic chance &/or should be pushed are: Fuko, Keira, Momoka, Airi, & Yuihan.
Fuko & Keira are the only two I follow to any extent in Team M.
But that is not the only reason I list them here. Looking the the audition footage above, Keira really stand out to me; she can sing & dance Really Really well, & was only 11 year old when auditioned. I believe Aki-P referred to Jo as "the next Jurina" or something, & I do recognize that Jo was a very hard working member. But just by raw talent & skill, I think Keira would fit the title "the next Jurina" a lot better. Of course, whether she can handle as much pressure as Jurina is unknown thou.
Fuko on the other hand, didn't have a lot of footage, barely actually, & from what little I seen... she didn't stand out.
However, she stand out a a lot currently! Personally I think she stand out a lot more then anyone else in Team M with maybe the exception of Jo. Additionally, from what little data I have seen, Fuko is Way above the competition when it comes to handshake event, registering 6/9h, only behind Sayanee, Milky, & Nana within NMB & way above the general flat zero of other members. Not only does Fuko look simply drop-dead gorgeous, her participation as one of the three members (along with Miru & Sayanee, who eventually advanced) for the NMB section of the audition for the Musical Yuka is gonna play, indicate she also have superior singing & dancing skills in comparison to other NMB members. If a comparison have to be made, & Keira is like Jurina, than Fuko is more like Matsui Rena imo.
Considering the above, who I would like to see as Team M's next aces is Fuko & Keira being double ace, with Fuko taking on a greater role. It also interesting to note these two seems to have good relationship.
Momoka is interesting thou; while her handshake sale was flat, her g+ & mixi rank much higher than her Team M peers! Her g+ registers 46,341 followers, only behind Jo's 51,843, while being much higher than Fuko's 34,778 & Airi's 30,527. (Speaking of g+, does anyone here know why Keira doesn't seems to have the g+ account...?) Also, Momoka's Mixi ranking is higher than not only Fuko's, Airi's, & Keira's, but Jo's as well! All this plus her crazy character make her a black horse candidate for ace of Team M. I don't think Momoka have a realistic chance thou, nor do I think she if fitting as center compare to the above two choice.
Airi is listed because I heard she's one of the more popular member in Team M. She is also one of the few I recognized (along with the aforementioned three) so I guess she's a possibility. Nonetheless, her data doesn't give her any edge against Momoka or Fuko.
If Yuihan is considered, than her popularity definitely crushes her competition.
Being from Kyoto also gives her legitimacy to take an active role in NMB, as Kyoto falls under the Kansai/Kinki region. Fans of Team M might not be appreciative of her taking center position however, & might prefer a "locally grown" member.