Nested thresholding for other multi-signature protocols

Determine which other multi-signature protocols admit nested threshold multi-signatures and characterize the properties required for such nesting to be supported.

Background

The paper introduces nested threshold multi-signatures as a way for a threshold group to occupy one signer slot within an unchanged outer multi-signature protocol. Iceberg demonstrates this approach for MuSig2, which is the multi-signature protocol used by the Lightning Network. The authors leave unresolved whether the same form of nesting can be constructed for other multi-signature protocols and what structural or security properties those protocols must possess.