https://www.punkt.ch/en/products/mp01-mobile-phone/
There are two features that would be very hard for me to give up though: maps and streaming music.
Unfortunately I have a feeling that "must haves" are different enough from person to person to make a semi-smart phone impossible.
Indeed, my "must haves" are pretty different -- I can live without maps (I can get around NYC pretty easily without looking at a map) and I don't even use streaming music as it is (I wouldn't mind carrying around an MP3 player). Hell, I could even go without a camera and it'd be fine.
What I'd want, though, is Facebook Messenger in addition to text messaging. Too much of my communication is based around it to have to go back to text messaging.
Also, as much as I hate to admit it, apps like Venmo really do make my life easier, and apps like Tinder seem to have become tragic necessities for 20-somethings in the modern world...
Edit: As a matter of fact, I have been wondering why we still have old SMS and not something like SMS 2.0 messenger worldwide.
Not sure if Multiple Numbers is a thing in US or EU. My guess is that most company are sane / clever enough to have a mobile number for their Employees. But here in Asia, it is common to have more then one mobile numbers, 1 for Work and 1 for Personal. ( Hence the Dual Sim phone popularity in China )
And it should be as slim as possible. It should be Appliance like Dump Phone and iPod instead of Smartphone or iPod touch.