If I were a player, and not an idiot (which I am, and I'm not), I would make sure when spending my 200,000gp that I coughed up 900gp for Oil of Slipperiness.
Because I'm not an idiot, I know what Snatch is, and I know how bad it's going to be for me to get grappled by a dragon.
Now, the previously-mentioned AM-Field on a dragon's claw would take care of that problem, and be a nasty, NASTY surprise
----
By the way, if I were adjudicating this battle, I would probably outlaw Wishes, Miracles, Gates, and Time Stops. Because:
1) Wishes/MIracles are a bitch to adjudicate -- unless all they do is duplicate lower-level spells. Even then, it's a bit wrong, because this is a one-shot combat, and the party members probably aren't going to care about losing 5000XP. Starting them out at only 1000xp above their minimum experience level is a good idea -- Wishes and Miracles will not be castable in this case.
2) Time Stop is one of those "Whoever casts it first wins" types of things, and should probably be Rule 0'd away for this combat.
3) Gates -- well, I think it takes awhile to cast it, in which case this might not be a big deal. But this battle is supposed to be between the Dragon and the 20th level spins. Not the Dragon's many cohorts and buddies against the (likely more numerous) party cohorts and buddies. Especially when we're talking about *Solars* and such. Regularly summoned monsters are okay, of course. Similarly, I'd ban Leadership.
Another call you're going to have to make is whether Dust of Disappearance protects against True Seeing (it probably should NOT) and whether Non-Detection foils True Seeing and See Invisibility (the official ruling is that it does . . . )
The Dragon, with his Blindsight ability, is going to detect whoever is within several hundred feet of him, down to the square -- I'm pretty sure.
The party will not have this ability. Meaning that if you can get an Improved Invisibility effect on the Dragon that the party cannot pierce, you will be sitting pretty. Dust of Disappearance is an option -- the range of True Seeing is only 120'. The Non-detection thing is probably even *better*, but I don't know what the saves for the party/dragon would look like. You'd have to do the math.
Of course, AM Field doesn't work well with Invisibility, does it?
