I think you can proxy just about anything if you want UDP, TCP.... there is nothing magic about proxies.
You receive on one end and send out the other.
Here is one quick easy "from google" example of a UDP proxy:
In DNS, assign the old server name as an alternate hostname to the new (Linux) server.
Yes I support that.
Have a speaking alias name in DNS like timehost or time1.
And for a migration you simply move the alias name in DNS.
Still you'll need to reload/restart ntp on all clients to make them aware of the change.