A different setup would probably make more sense for IPv6. Putting multiple /64s on one layer-2 domain isn't very useful. Just one /64 has 2^64 addresses. You could let each server pick addresses from a subset of the /64 for example. If the /64 is for example
2001:db8:aa:bb::/64 then server 1 could use every address between
2001:db8:aa:bb:0001:ffff:ffff:ffff/64, etc. That way you could fit 65536 servers on a subnet with 16 million addresses per server.
But that's still pretty much IPv4-thinking. What would probably be much more useful to your customers is if you provide a routed subnet per server so that they can more easily run things like docker and virtual machines inside their server. I would recommend at least a /56 per server. If you combine this with the addressing suggestion above you could route the prefix to the ::1 address of each server. So for server 1 above you could for example set static route
Then you are really using IPv6: provide plenty addresses on the LAN and give a block of subnets to each customer for virtualisation etc. Much cleaner and more useful to your customers than messing with multiple /64s on one LAN.