Social Security Number Monitoring
Dedicated detection for breaches of things like Social Security Number, Identity (license, passport), Credit Cards, etc. would be great. Unless I misunderstand the current interface it seems it will only find these things if related to a monitored email.
I think considering with the introduction of SimpleLogin there is already the concept of trying to protect your identity, it would make sense to wrap in more identity protecting features to Proton Pass. It could even be a separately purchased add-on like ongoing identity protection, but it would be nice if inside my main suite I could also have dedicated SSN/Identity protection. Oftentimes there are too many and it's annoying trying to get one that's dedicated.
And I'm sure it would be a business opportunity for you all at Proton, because I can't imagine people who are security minded and using Proton wouldn't at least be interested. If you're offering a service for identity protection, you already have a user base who would buy it.