As an ISP you are allowed to hand out my DNS64 addresses to your customers as long as you comply with the following requirements:
You can hand out my DNS64 addresses to your customers using router-advertisements, DHCPv6, or by other means.
I cannot provide guarantees about bandwidth availability. Howeever there is a few pieces of information you can provide me in advance to improve the chances that I'll be able to accommodate your traffic:
I will share your estimates with the transit providers unless you explicitly ask me not to. To the extend the transit provider will cooperate I will perform load tests to ensure sufficient capacity to accommodate your estimated traffic.
If I have to prioritize traffic due to capacity reasons the following criteria will be taken into account in guiding my decisions on who to prioritize and who to throttle:
If you wish to have DNS64 hosted on your own network you can provision an Ubuntu 20.04 machine (virtual or physical) on which I can operate a DNS64 server which will hand out addresses using my NAT64 pool. Administrative access to the DNS64 server will be shared with both you and me having access.