[mQu]

Yes and no. In my tests with live traffic (fingerprint,ip) tuple was as good as standard tracking cookie. Sometimes even better because I could match "incognito" modes as well. This was however only for desktop browsers. Mobile has much higher conformity and yielded mostly false positives.

YMMV of course but for my purposes it was not worth it.

[the8472]

I imagine ipv6 would drastically reduce the chance of false positives for collisions.

[hrjet]

Yes and No. The client could hop over a bunch of ip6-addresses, since there would be an abundance of them.