Warmage Rainbow Servant question (3.5)

[flappeercraft]

So if someone started as a warmage and used it to qualify for rainbow servant, could he cast cleric spells spontaneously by the 10th rainbow servant level?

[Thurbane]

So if someone started as a warmage and used it to qualify for rainbow servant, could he cast cleric spells spontaneously by the 10th rainbow servant level?

Yes. This is a fairly well know high op/TO build: the Rainbow Warsnake.

The most often debated part of RS is the casting progression i.e. "text trumps table".

What most often confuses me about this build is why you wouldn't use a better chassis like Beguiler instead.