[refset]

> use symmetric crypto

To be clear my comment is specifically only relating to signature schemes, not encryption.

> The state is enormous

The scheme I linked to points towards efficient "pebbling" and "hash chain traversal" algorithms which minimize the local state required in quite a fascinating way (e.g. see https://www.win.tue.nl/~berry/pebbling/).

> tracking state across components and through distribution channels

Assuming you have reliable ordering in those channels I don't see how the stateful nature of such schemes makes it hugely more complex than the essential hard problem of key distribution.