Hi,
I suggest you consider Standard_M192idms_v2. Specifications are similar to what you have now, except RAM is increased to 4 TiB and vCPUs are reduced to 192.
Based on specifications, you should be able to resize from M208s_v2 to M192idms_v2, however, whether or not the resize will succeed will depend on available capacity. It is possible I missed an incompatibility between the two when reviewing the specs, but based on my experience with main factors that block resize I don't see an issue.
You may also want to consider Standard_M208ms_v2, which has 5700 GiB RAM, but at higher cost than M192idms.
Msv2 and Mdsv2-series Medium Memory
https://learn.microsoft.com/en-us/azure/virtual-machines/msv2-mdsv2-series
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP