As a Tizen user, I believe that one of the most important improvements Facer could make, is to enable the "Dim" watchface on Gear devices.
At first I though this was a problem I was experiencing, but as I found out all Gear sers (with Tizen) have it. Support simply said that it wasn't possible for Tizen, however, other apps such as WatchMaster that is also available for Andorid Wear, do enable multiple "Dim" modes, so it should be theoritacally possible.
Other than that; I guess just reliability across platforms for Complications (eg. activity counter)
I'm really enjoying Facer and how complete and flexible the creator is!
Keep the good work coming.