Woah I didn't even know this was a thing :O
Is this the kind of effect your referring to??
http://www.effectgames.com/effect/article-Old_School_Color_Cycling_with_HTML5.ht...
Yeah, overall palette offset would definitely be a useful/interesting tool, but more of a radical effect.
Another possibility would be allowing cycling between X number palettes on a per frame basis?
That way you could manually make X number of subtly different .ASE palettes and cycle them?
Perhaps this would be easier to implement?