I don't sure this plan will affect to the system or HA.
Please help me revise this plan or suggest me about this situation.
Both F5 don't set VLAN failsafe and use network failover on the interface 1.8.
i do not think it will affect ha because heartbeat is over interface 1.8.
by the way, you know the best practice is to configure both tmm and mgmt interfaces for network failover unicast, don't you?
sol14135: Defining network resources for BIG-IP high-availability features (11.x)
https://support.f5.com/kb/en-us/solutions/public/14000/100/sol14135.html