I used to leave the house with just my watch and it was great - I could read and send text messages, email, even take calls on my watch and have everything synced up to my phone at home. You can even download music to it and pair it to your airpods.

The missing piece here is just having a dumb phone - somehow I think that with some ingenuity you might be able to something that serves 80% of your needs here or something like that.