Party Support, LET'S DO IT

[Daniel_Hatcher]

On that note, does Scherzo/Migawari prevent Zantetsuken from K.O.ing you on Avatar/Einherjar Odin? (Never have done either)

It's a death move, it deals no damage unless you heal as far as I know, that can only save you if it deals damage.

[Hashmalum]

Didn't float in previous FFs actually make you float, and therefore immune to earth elemental attacks?

Not precisely; certain attacks were flagged (or hard-coded) to miss floating targets and these were usually but not always earth-based attacks. Other things float status did were making it so you wouldn't take damage from walking over lava and such, and making it so you wouldn't spring traps by walking on them. Obviously neither of those really apply to FF11 either. I can think of several things float could plausibly do here:
1) Strong vs. earth attacks, possibly with a corresponding weakness to wind (I think FF9 did the latter). Not real likely that one of the six "major" elements would just get suddenly and arbitrarily hosed.
2) Anti-gravity (+evasion and +movement speed). Considering that we can already Sleep/Bind/Gravity mobs to keep them from catching us, I think SE might be afraid to give us yet another such tool. I sure wouldn't mind though!
3) Prevent the player from leaving footprints (your feet aren't actually touching the ground after all) and thus foil tracking by mobs that track by sight, making it the missing counterpart to Deodorize. This would be sensible but no one would ever use it.

Of course, there were some times in the FF series where it was actually beneficial to cast the spell on enemies. What would a float enfeeble look like?
1) In FF8, Selphie's "Rapture" special was Levitatega in the JP version, where Float was Levitate. Rapture lifted the monster up off the screen never to be seen again, presumably to Heaven or something. Tonberries were immune (I always pictured a sequel to "All Dogs Go To Heaven" called "All Tonberries Go To Hell"...) SE wouldn't give us instant death (unless it only worked on trash mobs at some low hit rate) but lifting the enemy high enough off the ground that it was rendered unable to move--sort of like how Break is an different elemental alternative to Sleep, this would be an alternate Bind. This could work but wouldn't be very interesting.
2) Again in FF8, in order to stop the earth-powered minotaur brothers from regenerating you had to remove them from contact with the ground by casting float on them. Accordingly, earth-based mobs could have their connection to the earth weakened this way, lowering attack, defense, earth magic attack/accuracy, TP gain, or whatever. Again, not real likely that one arbitrary category of mob will just get suddenly hosed.
3) Make the mob weak vs. wind (but strong vs. earth). I guess it could work but again would be kind of dull.

[Babekeke]

We actually already have floating mobs in this game (well flying mobs). Perhaps casting float on a non-flying enemy would make it immune to melee damage but take doubel damage from magic/ranged? Probably be broken though.
As would making it enhancing, and casting on players would make them immune to melee damage. Unless, like in the OP it was for a very short amount of time with a long recast. Now I look at it from this angle, this is probably what he was thinking, duh >.>

[Aliekber]

Pretty much, yeah.