Nested Virtualization Tips

I totally agree, the cost tracking and ease of inviting users is tough to beat, and I'm watching closely because my customers also want this capability. Unfortunately, I haven't heard anything definitive on it yet. 

For DevTest Labs, you might consider checking out shared image galleries. Set up a gallery, image, etc. and then you can share it out. You might find it easier to create the gallery in regular Azure first and then share it out to use in DevTest labs. Inviting other users is not as simple as with ALS, but it might fit your needs. I'm hoping the two will either merge or the capabilities will overlap eventually.

Check out this article on sharing out the galleries: 

Share VM images with Shared Galleries - Azure Virtual Machines | Microsoft Docs