More and more customers are wanting coupled integration with Sage 200 / Standard using the API from their e-commerce sites so this is getting to be an urgent requirement for a lot of developers.
This then requires a service to written to get orders into Sage and stock items out etc. (at a very basic level)
Using your API as it stands it does not support the grant_type of "client credentials" when authorising to the https://id.sage.com/authorize endpoint.
This poses a significant challenge for non ui service type programs trying to use your API as it requests a login via a GUI interface and as I have recently found out, the refresh token also expires so you cannot login once then use the refresh token to get a new token (and a new refresh token with a new expiry) to continually use the API without having to login again.
Implementing the client_credentials grant type would allow developers to write server to server programs and login programmatically and thus keep customers from moving away from using the Sage API due to this limitation.