This is actually mostly a security question.
Point 1
The only way an SSH proxy can be useful is when the target host stays behind public network, such as the following:
+--- Office Computer 1
Internet <--- Router-NAT-Firewall <--+--- Office Computer 2
+--- Linux Server (no port forwarding)
+=== Windows Server (with SSH port forwarding)
Otherwise, your Windows server is just an actor playing in a security theater.
Point 2
SSH is a very useful transport protocol for applications, you should maximize its security by mandating users use public-key cryptography to authenticate themselves.
In "sshd_config":
Use the "AllowUsers" directive to select the users allowed to login from SSH.
Use the "Match" directive on the selected users and use "AuthenticationMethods" directive to restrict them from logging in with passwords.