Topic says it after all.
Since many people move away from the one source that was reliable for years but got worse in the past years and the rise of many new sources and options out there, it would be nice and interesting to see a mdblist integration for syncing to keep track of personal collections. Many systems can sync to mdblist and build your collection, so SeriesGuide could pick up this list of your collection or other lists you define and sync.
I don’t know how complex this would get, but I know the guys over at mdblist are very kind with developers and many other tools already have an integration with their API.