Irule to persist all traffic to only one pool member

Hello, I am trying to figure a way to support this requirement We have 6 pool member and only one shall get all the requests, if one Node1 fails Node2 shall get the requests (then Node3, ...) traffic only goes to one node at any time.

Prio Group activation is not an option because a failback should not happen if a member comes up again

We wanted to have a mask of 0.0.0.0 to have a persistence for ALL src-ip

Splitting the client to 4x VS and add each subnet as src-ip persistence is not an option

Can anyone think of a way to do this within an iRule? The issue we have is that we only have the one DB server, which sits the other side of the app server(s) or pool members from the F5 side.

Along the lines we use an advanced monitor to query the backend db and sent a request and get an expected response, traffic is persisted to that node, if the monitor fails, redirect all traffic to the pool member where the monitor now works.

Thanks if you can help me figure this one out.