Well, prefix delegation would be fine as long as the ISP guarantees that the delegated prefix will be stable. But they aren't guaranteeing that unless you pay e

Well, prefix delegation would be fine as long as the ISP guarantees that the delegated prefix will be stable. But they aren't guaranteeing that unless you pay extra for a static v4 (because they're tying v6 assignments to v4 assignments), which is indeed asinine.