I'm getting quite close to finishing a 20 level progression of the Swiftblade, focusing on martial skill that's greatly amplified by Haste. There are also a few unique twists to Haste, such as increasing the bonuses to attack rolls, AC and reflex saves by reducing the length of time Haste is active or using Haste to grant fast healing and enhanced poison resistance due to rapid metabolism. These would be actual abilities, similar to how a bard uses Bardic Performances). I'm especially excited to see people's reaction to how the reflexes of the Swiftblade become intregral (beyond merely the Arcane Reflexes of the original Prestige Class).

Anyway, originally, I intended to make Haste a spell-like ability that starts off very weak (personal range, reduced effects and reduced duration) but eventually becomes an extrordinary ability like Rage. Yet, as an alternative, I figured a very limited spell list would be welcome for those that want it. Which is where I'd like some help. Assuming that the Swiftblade would mostly only have access to movement enhancing buffs, what kind of spell level should the Swiftblade stop at and are there any obscure spells that would fit?

This would be a Tier 2.5 class, by the way. Powerful, yet focused, and rewarding for those that go the whole way.