I have been working on a design for Bitcoin sidechains using the Tendermint
BFT consensus protocol, which is commonly used to build proof-of-stake
networks (Cosmos is the notable one).

The design ends up being very similar to Blockstream's Liquid sidechain,
since Tendermint consensus is not far off from Liquid's "strong federation"
consensus.

Any feedback about improvements or critical flaws would be greatly
appreciated. The design document is here:
https://github.com/mappum/bitcoin-peg/blob/master/bitcoinPeg.md (that repo
also contains a simplified implementation of this sidechain design).

Thanks for your feedback,
Matt Bell