You can tag partner with anyone, but the difference is some have special tag throws and poses. Gen Fu already has this with Helena.
Free Step Dodge
Xion
makoto
Pai beneath the Sarah, Gen fu beneath the Helena and Leon beneath the Mila
Xion
not sure what im supposed to be noticing but I guess youre speculating on how the final select screen will be organized. It should be 24 players in total with one slot being either leon or alpha 152
makoto
No, the vertical slot means partner i think. you understand? =D