IPv6 Failover or advice with solution

Hello,

we are building HTTP HA Load-balancing proxy using two servers in OVH and Failover IP. The IPv4 is crystal clear, but the problem is with IPv6. So, my first question is, if is there any way how to obtain Failover IPv6 from OVH? I know that IPv6 is assigned with HW by default. I am asking, if its possible to do that individually, on demand. If this is not possible, can you guys give me some tips or advices how to make IPv6 available for HA HTTP proxy without having multiple IPv6 - one for every node, in DNS and multi-master proxy? The architecture will be HAProxy on node1, node2 to distribute traffic between VMs, one failover IP routed and if any node1 goes down, corosync/pacemaker make failover and move the FO IP.

Thanks in advance