I've worked with different OS versions running in prod, it was just fine from a DM perspective.
Different OS versions can have different password complexity requirements for users, this might lead to some to users not in sync,
but not something a good IT team cannot sort.

So I'd say yes - as long all the OS versions you use in the cluster are all included in Skyline's support
(and far from end of life - Win2012 should be ok till 2023 - plenty of time to plan a DMA migration).
HTH