In terms of what they do with big data there's more evil parties like Palantir but data abuse starts with collecting it, and I would object to it even if Google promised to only use it for good. For me my privacy is already violated when my data is collected, not just when it's abused. And I do consider Google's use of that data abusive, just not in the worst ways.

I think they could make that significantly more difficult by adding csprng delays and padding to the messages. That way you can't really effectively correlate timing and sizes without direct access to signals inner workings. I'm not sure what signal's actual throughput is, but if think as a paid feature it could be economical.

Another crazier way would be to send every message to a large number random latched recipients. Good way to 1000x your bandwidth.

> The metadata is as valuable as the data.

This can be true if you are able to get ahold of a user's device and access their signal messages. It's not true in most other cases. I don't particularly care if you know that I am talking to someone specific as much as I care that you don't know what I'm saying.

If this is part of your threat model then I would suggest a different tool such as SimpleX since it uses onion routing and can be configured to always use private routing/relays.

Competition is Qubes but that has usability issues and does not have good hardware security.