Yes, I came to a similar conclusion about Liquid as a mixing service, here are my notes:
A federated sidechain network with cheaper, faster and confidential transactions. The federation is controls a multisig wallet. To peg in, one can run a node and make a BTC transaction into an address owned by the multisig, with a claim script to validate the liquid tokens on the other side. To peg out one must go through one of the federation members either through an exchange or a swap service like https://sideswap.io. There didn't seem to be peg out limit on that swap service but I haven't tried it yet The conversion rate is 99.9% so you're paying a 0.1% fee.