Blockchain makes a ton of sense as a replacement for the NSCC which is the entity that actually keeps track of the ledger for ownership. But again whenever I say things like that the people that come out of the woodwork are crypto bros vs skeptics which this isn't about the cyberpunk antigovernment anonymous future but just a better cryptographically proven multiparty database.

I would probably make trade settlement faster and lower overhead costs.

Clearing equities trades with a blockchain between brokers would be beneficial in plenty of ways that are really only all that interesting to very large banks and broker services companies. (like Citadel for example)

https://en.wikipedia.org/wiki/Depository_Trust_%26_Clearing_...