I think I have an Idea of the next Melee Class!

[Shougun]

They are also in the artwork for the new dungeon, with the oldest sister holding a scythe.
And to be clear I don’t think they are going to be a job in the game, I just think his shirts were akin to his Bugs Bunny shirt in 2018.

Also the to piggyback off Charon, the Sisters are based on the furies that also guide souls to the afterlife.

With them also being fought in the Tower of Zot in FF4 I don’t think it’s a leap any more than the thought of a “reaper” class in a final fantasy is.

That magus may be coming, I don't that is a leap, that the shirts were for them I do.

Bugs bunny was for Viera, a pretty legendary announcement to make. Maybe it is just me but Magus sisters being added to the game literally adds nothing for me. It's not exciting news, or sort of news to care about, like Anima being added who is a big deal.

The artwork that may relate magus only makes me think of Ranjit like situation even more since one had an elephant, adding further to that whole Sanskrit potential situation and as you said furies (making a job that is in essence Charon even more likely, The Fates are not like Charon (and they don't guide souls, they weaved fate hence they were called the Fates) - so there isn't an issue that both exist, if anything it supports it since the reference material of Fates obviously has a Charon). Of course other than Charon there is also Thanatos, they have some overlap in duties sometimes (Charon more dedicated guide obviously lol).

Viera = big news, worth a shirt
Magus sisters = ....kay? The possible evidence that they are coming I think is fine (from that other artwork), the evidence they are the shirt's reveal.. eh I just don't see it. I think if that was the reveal then Yoshida just made his shirts far less interesting to trust as big news. Shirts now could be introducing minor information. Especially given the situation they revealed Anima straight out already, a bigger deal than Magus sisters (making saving the shirts just for them seem even more, "are you trolling us?" If that was the case).

Although like I said maybe I missed some legendary aspect about them (perhaps there is a huge fan base out there, to me the Sisters are just goofy characters with minor background stories that have showed up a few times- nothing that interesting). Still seems of a leap over other options, imo.

As for the reaper part not sure where it is hard to imagine, except maybe for the fact it is called reaper? Of course they'd probably call it something else, especially if we're going with all this Middle Eastern / Indian influence (god of death for Indian's is Yama, Cindy in that art work, if that's Cindy, has an elephant head like Ganesh which is not a Yama feature), but the job concept of what a reaper does is noble and good (in the essence of order, duty of psychopomps).