Characters you wish they would have been Guests

[Sephiroth]

Dash, FuSoYa, in a way Theodore for the final battle, Banon, even Leo, Sephiroth, Seifer, in a way Laguna, Ward and Kiros, Edea, Beatrix, Seymour, with him just running through the prologue Reks, Vossler, Reddas ...

There are so many guest characters in Final Fantasy which often had a very stylish way of being shown when they were in your party. Of course I don't mean characters like Aerith, Galuf or Tellah who actually where a real party member for a long time but then died. The ones mentioned above are what I talk about. Actually even Laguna and his team is an exception since they have many story parts so I only ~ call them "guests".

Which characters would you have wanted to be guest characters in your team?

More of the main villains in a cool scene which should demonsrate their powers like Sephiroth and Seymour's scenes did? Characters which have shown skill but were never really shown in a real battle ingame-battle-wise and story-battle-wise? Or maybe other characters you have found interesting but which were not shown enoug, so not only battle-wise?

And did you want some of the guest characters which actually were guests have to be longer in your party? Or even for a shorter period of time?