At present there is support for a virtual CME via CRS1k. However, this CME can't function as an SRST (fallback for when CUCMs aren't available to endpoints on-site).
This means having to keep an ISR on-site for registration redundancy whilst there is an existing virtual router which could theoretically have provided this functionality for us.
I would also like to request that should this idea go under review, that HA support between twovCubes also support the SRST functionality.
Thank you for your consideration.