And not sure how dev testing software in real would require domain admin
Our software is used exclusively in AD networks, so testing involves having servers that are part of the domain. When you're testing with virtual machines that are part of a domain and you roll back to a previous snapshot, the domain trust is broken and you have to remove and then re-add the server to the domain. Plus, our solution relies on Microsoft DFS Namespace support, and I don't want them playing around with that on our real domain. That's why they need domain admin for some things. I know that I could probably design something else but this is the way it's always been done since before my time, and I'm planning on redoing EVERYTHING this Fall when Server 2019 comes out, so I'd rather not make any changes to what we have that works now.
Mainly the split-DNS issue.
OK then, I'm not concerned. I literally have two NATs to worry about, so split DNS for those will take 2 seconds to create and will likely never update.
I think I will stick with the single forest-single domain model. Thanks again, guys.