I think i2p support makes sense. The only tricky part is what prereqs that reuuires. For an individual building torsocks, they'll either have or not have tor and have or not have i2p, and they can be detected, and that's fine. For a packaging system, the package has to have dependencies chosen, and this leaves the packager choosing wither to leave something out or inflict the dependency on everyone.
If torsocks doesn't need tor installed, because it just uses socks5, and similarly for i2p, then there's no issue - this sounds good.