It's incredibly unfair to the rest of the PC cast, and way too convenient for temps. Yay, she's overpowered due to an entirely situation-based scenario that doesn't keep up as the game advances, and, as a PC, she wouldn't be able to enjoy it were she to stay as a permanent PC due to the rest of the cast catching up. Beatrix with endgame levels and equips scaled against an endgame party (which is how I tend to take temps as a whole) wouldn't have this. By that logic, you may as well take Rune as his overlevelled earlygame temp form.
Taking temps to some imaginary situation where they live/stay in the party to be an endgame PC doesn't strike you as twisting the actual game? I mean, if I said "Belial's damage sucks at endgame" but scaled temps to the time they leave I would expect to be called out for it. As far as "Cherry picking" goes, I hear no such accusations against people who hype earlier forms of bosses that are better than their last/later appearances. Ultros comes to mind, and so does Jeremy. (I would take the last temp appearance in most cases, with possible exceptions like Asch where the temp appearance is a remote sidequest where it is tossed in)
Scaling temps to the time they leave is no different from scaling bosses to the time they are fought. As far as damage caps go? A midgame SO2 boss who overkilled by 3x (you can stop laughing) would be taken as such, and most anyone who went "But endgame bosses can only do 1.1x overkill or so!" would be ignored by the majority. Same philosophy applies for Dhyer and myself. You are free to have a different opinion but nothing you say is going to make it objectively right. Bear in mind that the view you are espousing is the one that is the one that is essentially creating an imaginary PC that is present at endgame. Also see Dhyer's comments on Miranda/Alonso.
Godlike:
Ryu (BoF4) vs Beatrix (FF9): Still thinking. Ryu couldn't get any Holy Resist? That surprises me. Also: *IS* Dhyer hyping something other than the last temp appearance here?
Cecilia Lynn Adlehyde (WA1) vs KOS-MOS (XS): Prison I guess.
Lavos (CT) vs Teepo (BoF3): Any match with Lavos is a headache, but I'll just nod smile and move along.
Heavy:
Kevin (SD3) vs Zeno (BoF5): A good shot of OHKOing damage or whatever should do it.
Fayt Leingod (SO3) vs
Nel Zelpher (SO3): Has healing.
Poo (EB) vs
Angela (SD3): Poo's chance of winning through status is 40%. Angela's is 60%
Middle:
Ena (FE9) vs Lucia (Lunar:EBC): Lucia is ranged so the boss form is screwed. PC form... Oh for the love of... I think her PC form wins. Ah screw it. I'm going to get a drink.
Kornell (G3) vs Caellach (FE8): CORNELLLL BUSSSSTTEEERRR.
Eiko Carol (FF9) vs Volke (FE9): Eiko isn't 2HKO'd by Volke regardless so just smites his horrible Res with Mini and Holy's him into oblivion? Dunno about speed, but I guess that should work.
Light:
Cleo (S1) vs Wil (FE7)
Yukari Takeba (Pers3) vs
Taya (SF2): Does Taya OHKO here? Might have had Lightning damage? One or the other should work, I'll look later.
Alenia (S5) vs
Kid (CC): It is Alenia.
Mukumuku (S2) vs
Peco (BoF3): Peco looks like a god here.