No coffee yet so forgive me if I seem confused.
1. Levitate potions are no different than having a caster cast levitate on you. This would be a convenient and great thing for people without levitate items, classes that can't cast levitate, people who like to make potions and people who like to drink potions. I can't see the downside unless its some "player interaction" thing, and if so why are there so many potions and items that apply interactive abilities from other classes?
2. Illusion potions wouldn't cheapen Fame Point illusion rewards any more than awesome Fast and the Furious body kits on Hondas cheapen Lamborghini and Ferrari. I offer as the proof for this argument that nobody uses Fame Point illusion rewards (except maybe race change, and even then only a few people), and that sb perma illusions already do circumvent the need for them completely, even.
Now is the part of my post where I shoehorn in the idea of race changes as a free gift for your donation of more than $x, or 6 months of platinum, or mailing a brick of rhodium to SoD HQ.