Better than that, build an anonymity network with both mixing and onion routing, and full padding with chaff. And implement it as drive-by malware, with worm capability. Like WannaCry. It'd be basically a huge botnet. And it would use a covert channel in HD video, which would provide enough bandwidth for text, at least, and maybe images.

That way, participation by servers and clients would be plausibly compulsory. Both because it would evade protection, and because sympathetic admins and users could "accidentally" let it install. And that would provide plausible deniability.

A plausibly deniable user interface would be the hardest part. It'd probably need to self install, and then securely delete itself after use.

> It would be hard and would likely attract only technically-minded individuals

... and police forces: a nice feature of leaving a few gaps that motivated users can use is that the police can focus its limited resources on the those interesting targets.