Hello good people of Tor. As you know, your client side applications like Tor browser are unmatched by anything out there. They are the natural choice for other anonymous networks. Freenet is considering ways to interface with Tor browser for better privacy.
Disclaimer: I am not an official spokesperson for them.
I am testing the waters first before filing tickets on trac.
My idea is for Tor browser to include the FoxyProxy for redirecting browser requests to proxies based on URL patterns. Optionally there's color indicators for every proxy so users know what network they are visiting. You can add rules to block LAN accesses to keep users safe from misbehaving JavaScript. Rules can be added for I2P URLs too.
You'll need to disable the ads in the original addon but the code is DFSG compliant.
Like the transports, your client side applications are a new area for collaboration beyond your project. What do you say?