This was such a sneaky-good feature with Mailbox (before Dropbox shut it down) and solves a bulk of my priority / triage problems with email. I've surprisingly had a difficult time finding any other client that can do this.
...Though, knowing HN, I'm sure someone probably has one up their sleeve =)...
This allows me to have business actionables on top, then personal actionables, then unfiled bills, then new incoming messages.
I'm a huge fan of Mail.app, but my biggest frustration is that the colored flags don't carry to my iPhone (the latter of which only has one color flag in the Mail app.)
My other response is that I'm big on stack-ranking tasks / priorities, so your flow would be great for personal stuff, but not best for what I need for work.
You can also use 'super stars' to accomplish multiple priority states within starring.
Here's an example of a real power user: https://medium.com/@gregsramblings/how-i-tamed-gmail-at-work...