Hi,
I think I got the point.
Well, If create it in zonerunner you have simple dns BIND records and maybe it can't work for your need (same record for different topologies).
If you need to reply by topology dependency (internet/intranet), you will need the GTM intelligence.
An iRule could solve this or also creating servers and virtual servers on GTM/DNS to balance and send best choice replies.
But, I can't see a need to create LTM layer, then just a GTM layered objetcs to do this job.
You just need to setup a existent address to a "Generic Host" on GTM server/vs
Got it?
Best regards