Along these lines: CashTokens enables trustless proof-of-stake sidechains run by sets of cashtoken holders. Withdrawal transactions can be processed on an interval by a vote of token holders + "enforced vote secrecy" https://github.com/bitjson/cashtokens/blob/master/examples.md#sealed-voting
Works just as well for a prediction market as it could work for a trustless mixing service, effectively like http://Tornado.cash, but doesn't have to be written in a blockchain VM language, you can just write the thing in Rust or whatever (the only mainchain consensus code is some simple covenants + CashTokens)
So more plainly: you can launch Zcash/monero clones as proof-of-stake sidechains, and deposit/withdraw BCH whenever
(and atomic swaps work between the chains)
The gist is that we can do the same withdrawal process as Drivechain: https://github.com/bitcoin/bips/blob/master/bip-0300.mediawiki, but instead of having miners vote, the cashtoken holders vote. Vote coordination is discouraged by the sealed voting idea from Truthcoin (page 43) https://bitcoinhivemind.com/papers/truthcoin-whitepaper.pdf
So there are 3 types of assets: BCH, sidechain "shares" (cashtokens), and sidechained-BCH (BCH that is locked in the covenant and currently being used on the sidechain). More info: https://drivechain.info/literature/index.html
An unlimited number of such sidechains can be created, they just need to grow a large enough shareholder base that a single person controls no more than 50% of the token. E.g. even if group of fraudsters owns >50% it's still secure because one of the groups members can profitably double-cross it. All that matters is determining whether a single rational actor has a majority stake. (Page 25 here https://bitcoinhivemind.com/papers/truthcoin-whitepaper.pdf)
-- Jason Dreyzehner on Telegram
PoW version:
I think we could use our Script + CashTokens to implement BIP300-like hashrate escrow, too.
Hashrate would opt in by using a simple one-time vote covenant (OTVC) address that requires bridge DAO input as sibling.
Bridge DAO could then burn and tally these one-time vote covenants and accumulate them in NFT's commitment. By "unpacking" the TXID of the vote covenant's input, the DAO can verify the vote is indeed coming from a coinbase TX, and extract the height from the input to verify belongs in the voting window.