That sounds like a great feature, but I don't know if I'm able to pull it off.

Lets brainstorm here for a bit. I could however try to create a website which allows users to create their own lists and have EasyList sync with it with the press of 1 button.
Ofourse then there would be a need for a place to save the login credentials in the EasyList app. This would be a one-time thing. Once setup the sync button should work.

It would be even better to have an SSL connection, but is there a need for that for simple lists... I don't really think so.

Creating the website would take a bit of time as well as designing the protocol between the website and EasyList.
On the website you should be able to create your lists. All of these lists are going to be synced with EasyList. On the website you should also be able to make one of those lists as the selected list. That way EasyList loads that list.

Problem with syncing is always who should overwrite who when there is a conflict. I could make it easy for myself and let the user decide. Or make it harder and save change timestamps for lists and have the newer overwrite the older.

Or a completely different approach is to have only one list on the website. This list always syncs to one specific list name in EasyList. The website list always overwrites the app list.

It's a very interesting idea, but I don't know if I will ever find enough time to implement this.