I love all the Mother protagonist but I literally don't see a reason for Ninten as a representative of the Mother series. Just from based off what I have seen, Earthbound Zero although not generally hated, it's not universally loved either. It's a game people usually just play because they love the Mother series overall but very rarely will you see people call EB: Zero their favorite in the series unless in some cases, it happened to be the first game they played in the EB series. In addition not only would he just be another semi-clone like Lucas (same special moves with difference physics. Instead of PK Rockin, he'd have PK Beam. Slight variation to tilts and smash attacks), he also looks exactly like Ness and it's very clear that Ness's design was based like 99% off of Ninten.
Also don't take my word for it but is Ninten's scarf even kind of Ninten's "thing". Like not like it makes a big difference either way because a scarf will hardly differentiates the characters but I thought the scarf was only shown in the EB: Zero trailer. Also playing through Mother 1 right now and he doesn't even wear a scarf, perhaps he gets it later in the game because I've been preoccupied with multiple of other games. On the other hand as much as I love the Mother series, I think Ninten is possibly one of the worse options you could ever choose as an additional representative to the Mother series.