Hello @dufour_francois
Unfortunately, the option that you are asking for a few users to be authorized with time restrictions and some without is not possible even with the APIs. In order to achieve this, I would recommend either using an AD Server or Radius Server for client VPN auth so that you can configure the policy for time restricted access on the server when any user tries to authenticate.
Let me know if you have any questions.
Regards,
Meraki Team