Blockcerts Rebooting Web of Trust topics

I'm following up on the VCTF telecon discussion last week, regarding
Rebooting Web of Trust topics for Blockcerts.

Some quick context -- Blockcerts (http://www.blockcerts.org/) is an open
standard for issuing, receiving, and verifying Open Badge-compliant
certificates on the blockchain. We're excited about Verifiable Claims
initiatives, and are eager to participate in this community.

2 topics in particular would be useful for the Blockcerts project at
Rebooting Web of Trust:

1. Advancing the Proof of Publication 2016 scheme (
https://web-payments.org/specs/source/pop2016/)

The PoP2016 specification is an excellent match for expressing issuer
signatures along with Merkle proofs anchored to a blockchain. The spec
claims it is not production-ready, so I'd like to reactivate interest in
it, and also discuss some extensions:

- Allowing the Koblitz Elliptic Curve Signature scheme (
https://w3c-dvcg.github.io/lds-koblitz2016/), which seems straightforward
- Generalize 'merklePublicationProof' to allow other Merkle proof schemes,
e.g. Chainpoint v2.

2. Associating a public key with an Identity Profile.

ref: https://opencreds.github.io/vc-data-model/#dfn-identity-profile-model

In the Blockcerts model, the credential recipient provides their own public
key (in advance of issuing) to the issuer. The notion of identity is
external to the Blockcerts project; it is assumed (and enforced in various
ways in implementations) that the issuer and recipient have a separate
means of establishing identity and transferring keys.

It is not obvious to me how a self-provided cryptographic key would be
expressed in the Identity Profile model, or if that even makes sense (i.e.
perhaps there is a more natural location in the data model).

I'd like feedback about whether these are (or can be crafted into)
interesting Rebooting Web of Trust topics.

Thanks!
Kim