4 SNAT pools or a gigantic one?

Ah, OK, I think I misunderstood. You do actually mean fully in-line. That is my preferred design in most cases. The overhead of routing other packets (not to be load balanced by LTM) is normally pretty low and it also provides a great troubleshooting and packet capture tool in a significant place in the network which can help even with issues/flows that LTM doesn't handle as well as those it does. Of course, on the flip side, all traffic now relies on the F5, not just what you are specifically load balancing. So, as ever, what you do will depend on your needs and requirements and the constraints placed upon you.

 

 

An alternative which you might find attractive would be to have the these specific servers in an isolated VLAN directly connected to the F5 where the F5 is the L3 gateway for the network. The servers have a default gateway pointing at the F5 or, in your case, a route to the Intranet subnets. They can have multiple NICs in multiple networks for mgmt, backup whatever, just route as necessary.