Daniel LakelandOk, so it was not hard to get i2pd running on the #guixrouter. And it has a way to limit the number of transit connections, so I can probably prevent it from eating up my connection budget, so i2p is a go for default services on the router.
The only issue I have is that it doesn't seem to properly create the /var/run/i2pd directory and give it the right ownership/permissions. Though it LOOKS like it should work... and the same mechanisms work for squid... so I'm a little confused about that. But once you manually fix that permissions it boots fine. I'll fix it later.