iRule access to route table

If your nexthops are distinguishable and consistent, the safest path forward would be to use LINK::nexthop for this (and in conjunction with LINK::vlan_id if necessary)

If you really want to pull the routing table in, you could write an iCall script to periodically read the routing table and set iStats variables then use an ISTATS::get call to pull the right information based on your key. But if I'm understanding your ask correctly, I think the LINK::nexthop approach is the best bet.