By L2 switch in CML running 15.2, I assume you mean IOSvL2? This is not a commercial product and likely no DE in Cisco has looked at it in several years. The current version being shipped on the CML 2.8.0 RefPlat is 15.2(20200929) and has been since at least the 2.2.3 RefPlat from May 2021. There is, however, an alternative L2 device that you might consider: IOL-L2 with the 2.8.0 RefPlat version being 17.15.1 (the 2.7.0/2.7.2 RefPlats ship with 17.12.1). But that really begs the question as to why you would not try the virtual Cat 9000 nodes, with images available for both UADP and Q200 NPU flavors. Current 2.8.0 versions are 17.15.1, with 17.12.1prd9 available with 2.7.0/2.7.2. The Cat 9000v is a resource hog, so you must allocate adequate RAM and CPU for it to run.
The other part of your question concerns whether you can upgrade images in CML. The answer is yes, with the easiest being the creation of a custom image that reuses an existing node definition. If you have the entitlement to download and run an image for a virtual switch/router from Cisco (or a third-party), you can upload to CML and add to the library of nodes & images available to you from the CML Canvas.
Disclaimers: I am long in CSCO. Bad answers are my own fault as they are not AI generated.
