Hopefully it will be the default once implemented. Everyone will benefit from compact protocol in the long run. Should have been done from the very beginning.
the API already is super simple, and low bandwidth could already work on retro machines (I had 6809 in mind when experimenting with it). The problem is e2ee, but we have the Pantalaimon e2ee proxy to convert unencrypted Matrix traffic into E2EE traffic for precisely this sort of thing :)