iRule/policy for round robin traffic

Why don't you just add everything to a single pool as the F5 has no issues if the IP addresses of the pool members are the same ?

From what I see you also need to rewrite the host and URI and maybe for this an irule will be needed (you can also use the "switch" way and not the "if" condition and you will need to add many elseif to match the other conditions):

when LB_SELECTED {

if {[LB::server addr] equals X.X.X.X && [LB::server port] equals 1001} {

HTTP::header replace Host "X.X.X.X:1001"

HTTP::uri "/core/services/instance_1"

}

}

https://clouddocs.f5.com/api/irules/LB__server.html

https://devcentral.f5.com/s/articles/irules-101-02-if-and-expressions

https://clouddocs.f5.com/api/irules/switch.html