More options for Filter Members

I love Ghost but it would be great if you could filter the members in more ways such as if they opened specific emails or not.

For example, I emailed my list to say the free trial was ending, and wanted to send a reminder a couple of days later, but I had to email all free members again as I couldn’t see a way to filter by those that hadn’t opened the first ‘end of free trial’ email.

Also these ideas about last login etc.