In GNS3, I went directly from the L2IOL device to the cloud and configured the switchport as a trunk, then made a few dot1q subinterfaces on the VIRL IOSv router.
I just played with it a bit more this morning. I added a GNS3 switch in between the L2IOL device and the cloud and captured the traffic. The ARPs weren't coming through correctly. It looks like ARPs coming into GNS3 lost their encapsulation. I tried switching the clould between Generic NIO and Linux NIO and got the same results. I am using VMWare workstation 11 on Windows 8.1. I verified that my host OS is showing that the virtual adapter is configured to support vlan tagging. When I get a chance, I want to test it on my Linux server to see if it exhibits the same behavior.
Just for fun, I decided to verify that I could get the L2IOU to talk to an IOSv device using dot1q via a L2TPv3 tunnel. It worked perfectly.
Realistically, I don't think the overhead for the extra L3IOU and IOSv routers is worth it for those who are trying to run simulations on their laptops.