@Simon_Cossar I just took a few minutes to research possible options to this challenge - and stumbled across you on this page WP Discourse – WordPress plugin | WordPress.org. So, I do have a more directed question for you about the plugin.
My business resolves around WordPress / WooCommerce and all my integrations tend to use tags, where they can, to manage users. WP Fusion is the glue that brings all this together but the bottom line is that I have tags on all users (whether customers, members, etc).
With that context, what I would love to be able to do is write my own function on the WordPress side that implements some logic (in my case, as simple as checking for a tag on the user) and rejects the logon if that criteria is not met.
Off the top of your head, do you know if there is any hook I can user that would allow me to implement that logic? That would be an awesome solution and leaves the logon still very much in the hands of WordPress.