Do you not have the ability to lease a static IP from the ISP for a nominal amount? From my experience this is always an option even on consumer lines.
Where I live (US), most ISPs won't give you static IPv4 addresses unless you are on a "business" plan. Beyond that, you also have to pay for those static IP addresses (it's ~US$25/month for 5 static IPv4 addresses, with one of those wasted because I'm forced to use the ISP's router, even though I already have one).
Perhaps where you are, static IPv4 addresses are available on "consumer" plans, but here not so much.
This is a problem with service. If the service doesn't want to fix it, then that sounds like a potential market opportunity, no? I'm new to thinking about the business side, but it seems like I want to remove any obstacle I can preventing a customer from using my service.
and this is why IPv6 isn't coming anytime soon, at least not within the next few decades.
You read comments here on HN every time ipv6 comes up how it caused great issues for them and they turned it off, but unless they are on a really shitty small ISP, it's their own fault because they don't use the router from the ISP but had to build their own setup and messed something up.
As people switch ISPs or get replacement routers that have it enabled, the world gradually moves over, and nobody apart from the nerds takes notice.