Thanks for your feedback mate, I really appreciate you taking the time and it's always great to hear what other developers would like to see in our plugin.
In regards to the suggested feature of a visual template composer, can you elaborate a little more on how you would like something like this to be implemented? Basically you'd like to see a visual editor that can allow you to add taxonomies/custom fields etc. to a template without editing the code directly?
As for the pro license, that will unlock all the limitations on the free version and will also guarantee that any future modules that come with the plugin will also be unlocked and fully functional. Here's a quick run down of the version differences: https://www.kontrolwp.com/upgrade
With the "image" custom field, I originally opted out of using the WordPress modal because it allowed me to incorporate a lot more advanced features if I didn't. Features such as automatic resizing, image effects (sharpen, blur etc), the upload progress bar, file size limitations etc. all wouldn't have been possible with the WP Modal. Like you mentioned though, the drawback of this is not being able to select an image you've already uploaded. I'll certainly look at this in the next update and see what I can come up with that will give us the best of both worlds. Might even give the user the option when creating that custom field if they want to use the WP modal for selecting or our advanced uploaded. Look for this change in one of the future updates, hopefully not to far away.
Thanks again for your feedback,