You could just do that on v14 which is out and stable vs waiting for v15 that has no real time table for being stable. Let’s be honest, there is no HA in v14+ right now because even in v13 it is problematic. I know someone that bought $30K worth of HA on v13 and had nothing but problems all on six instances he installed it.
At this level, Kamailio+FreePBX in Warm Spare setup is more than enough to deal with any failover on the network. Because with HA you still lose your calls and actually could lose registrations depending on the setup and how long it takes for things to jump over to the other system. At least with this setup, you just only lose calls.