Not really. Just a VS with tcp/389, SNAT if they're not routing back via the F5, translate IP and port (Or just IP actually should be fine if VS and servers are all :389). Persistence by srcip.
The monitor can probably be just a customisation of the built-in LDAP monitor (With the caveat some versions will follow LDAP referrals and mark the server as up anyway. You have to watch for that and customise to consider LDAP referrals as being down... Although that can be masked if the clients have the ability to follow the referrals AND have connectivity).
H