Some nice ideas!
Preview used to be a feature, but we removed that last-minute. The permission to preview an item was linked to the customer email. (If customer email = admin email, show). But as you can guess, what if someone just creates and account with an email that happens to be an employee? Yah, that’s a prob! So we have now begun testing on reading the back office cookie and check the employee’s status instead and use that for previewing.
Author widget is nice. We want to use Gravatar for it. No idea actually why it didn’t land in the first version. I think we forgot.
Yeah, language field should definitely be disabled for one language and have some defaults.
Yes, linking to products/categories should go both ways.
Shortcodes are awesome, but I don’t think the core is ready for it, yet. We’ll likely combine it with a widget system in the future.