A few options, but just as expensive as if you just got an ST2 from t get-go.
There are a couple aftermarket head-units and dash kits that will do the job, and still keep existing sync function too.
I think Alpine and Kenwood have sync compatible units.
Check out the electronics section and search for "metro Dash Kit"
Amazon has some good priced android based head units. Check those out. You can mirror link on them, and if you have a decent data plan and can tether off your cell - when you are parked bored...you can surf the web, email, social media... etc. From the looks of it the majority come with NAV as well.
Unfortunately you may have to wait to replace your radio. I don't believe anyone has a dash kit out for the 2015+ Focus. I'm waiting to put a remote start in mine and I'm running into the same problem. With the refresh there was a change made and no one currently has software for the 15+ so I'm stuck waiting patiently as winter approaches.