In preparation for the gathering this weekend, I finally hit the lab up for the first time, seriously figuring things out. I found some things out, but I also decided to see just how legit Nanaya's options after airthrow are. The following is a list below of Normals that work after a aircombo in the corner, either following one JBC, or two JBC's in the air. Obviously, Nanaya gets more meaty the lower to the ground the airthrow, so one JBC is far more meaty than two because of the height difference. All tests were done with the computer on recovery A, with the fastest normal possible their styles could allow; and all aircombos are assumed to be executed well with good timing. Without further ado, here's the list!
Nanaya's Meaty Approximations
Off a Single JBC in the corner
No real options at all, turns into a Yomi game = Ryougi
No Meaty, but Anti Mash [On Point Dash 2A] = Miyako
No Meaty, but Anti-Mash [Decent Dash 2A] = Ciel, Sion, V.Sion, Roa, Mech, Kohaku, Hisui
Meaty [If done really low with a On Point dash 2A] = Tohno, Nanaya, Warakia, W.Len[Hardest to Time]
Meaty [Decently Timed Dash 2A] = Warc, Len
Pure, Delicious Meaty [Free Dash 2A] = Aoko, Nero
Ridiculously Delicious Meaty [Decently tTmed Dash 5B] = Kouma
Stupidly Good Meaty [Easily Timed FUCKING 2C, no dash] = Riesbyfe
Off a Double JBC Airthrow in the corner
No Meaty, but Anti-Mash [On Point Dash 2A] = Vermillion, Akiha, Seifuku, Arc
No Meaty, but Anti-Mash [Decently Timed Dash 2A] = Tohno, Nanaya, Warakia, Satsuki, W.Len[Hardest to Time]
No Mety, but Anti-Mash [Easily Timed 2A] = Warc
Pure, Delcious Meaty [On point dash 2A] = Aoko , Nero, Len [Hardest to Time]
Ridiculously Delicious Meaty [On Point Dash 5B] = Kouma
Super Free Meaty [On Point 2C, no dash] = Riesbyfe
My list seems to mirror yours almost exactly, with the exception of both Lens and Miyako. Both Lens seem to be in a 'tier' a bit higher than you specified, though that might be me not being able to aircombo them well enough in the corner to be able to get legit meaty, as they have extremely odd airhitboxes. Miyako might be the same because of her small hitbox, but I had to be REALLY on point in order to not get mashed out.
I should also note that the meaty for Kouma and Riesbyfe because of their slow getup is so fucking free that Nanaya can 2A otg after a grab against Riesbyfe and 623B/C after a throw versus Kouma.