My thinking was that completely immutable functions map better to hardware that can't change its own design, but maybe it would be better to allow state sometimes. The problem with state is that it implies sequentialism.

Registers, signals, etc. can change values, but you can't change what they do or how they're used. So you can't really have anything like self-modifying code. But I guess allowing state would make sense sometimes as long as you are mindful of what the state is dependent upon. Making lots of independent little state machines would map well to hardware I think.