There are other issues to keep this opt-in. At least initially.
There are two issues.
A) Tor network capacity limitations.
The Tor Project expressed they preferred if file sharing isn’t used over the Tor network. References here:
Such continuous traffic would be similar.
B) Legal liability; courtesy:
Making all Whonix users use cover traffic by default would add additional automated (“robot”) Tor traffic. A lot traffic that isn’t even being looked at by any human, not even any program. (Solutions such as Proposal: add Noisy to default software simply discard after fetching a website or don’t even store it.)
Remote servers (websites) would received increased load. This could be considered a DDOS.
There might be a legal risk in doing that.
Also courtesy may require not doing that.
Maybe it would be different if noisy(or some other implementation) adhered to robots.txt standard that allows for an opt-out for websites.