Hey
From my perspective I would like to be able to choose role when a new member signs up. Maybe I want them all to become site-members at first and then I want them to be upgraded to premium-members and then I want to setup page-by-page which role can see the page.
I would be awesome if strips where like sections so I could set roles that can view certain strips or if you are at it at element lever. Maybe a button should only be seen by site-members but not for visitors. This kind of possibilities would rock.
But the most important is to be able to add an unlimited set of roles that we can use in code to make behaviour on sites different.
You can wish for heaven but just to add a new role to my site and then setup pages to that role or query code and collections depending on roles would be awesome.
If you then make it possible to add subscriptions or in some way interact with payment gateways through WIX Code and upgrade users from one level to another that would expand WIX.
I am full with ideas from creating hundreds of sites using other platforms so just ask me and I will pop out different thoughts 