Originally Posted by ZeroNumerous
It doesn't seem any more or less broken than Versatile Spellcaster, which does allow you to mix and match spell slots to get an insanity+1 level of 9th level spell slots.
No, it actually doesn't allow you to mix and match, it explicitly states of the same level
as well. And since casting a spell (for most spells) is a standard action, that is the amount of time it takes.
Perhaps a solution: Which Versatile Spellcaster are you looking at? I'm reading from the feat by that name in Races of the Dragon.