How to forward traffic to detached vlan?

VLANs are visible in management plane. It makes it possible to run local process that has access to such vlan (it allows to run custom applications on F5 appliance such as nodejs web servers). Is it possible to create vlan interface that is purely virtual (not assigned to any physical interface) and forward traffic to it from eg. ip forwarding vs? Ultimately I'd like to test one L2 analyzer "inline" by running it on F5 and forwarding traffic to it.

Final packets flow I'd like to achieve would be something like this:

world -> vlan_world -> ip_forward_vs -> vlan_detached_1 -> my_analyzer -> vlan_detached_2 -> vlan_lan -> lan

or functional equivalent. my_analyzer app forwards L2 packets in software (behaves like bridge). If necessary I accept solution using iRules.

For now the only solution I see is to use 2 conventional vlans assigned to interfaces and make short loop using physical cable but that would be waste of 2 interfaces which I'd prefer to avoid.