In our organization we use different BIG-IP DNS clusters for different environments, e.g. DEV has a BIG-IP DNS cluster, TEST has a BIG-IP DNS cluster, Prod has a BIG-IP DNS cluster. Generally each environment has it's own set of LTM instances which are federated with the environmental BIG-IP DNS cluster. This makes sense, as you generally aren't interested in the availability of a resource in DEV when making a query for a resource in TEST or Prod.
However our cloud gateway architecture only has Non Prod and Prod, making a clean one-to-one mapping from on-prem BIG-IP DNS cluster to cloud gateway LTM not available. It's outside my remit to stand up LTMs for use by DEV and TEST in the cloud gateway, so I am wondering if there are any issues with the DEV and TEST BIG-IP DNS clusters both being federated with a single LTM instance. I haven't seen any articles or manual content that says that this can't be done, but that isn't the same as saying that it can.
If you have done something like this in recent version (we're running v15.1.x), I'd like to hear if it worked well or not.