You should rename UI::[Non]Blueprintable to UI::[Non]BlueprintType and change comments accrodingly, because they act like UC::BlueprintType specifier, not like UC::Blueprintable.
And also you should remove CannotImplementInterfaceInBlueprint meta, and make proper UI::Blueprintable and UI::NonBlueprintable specifiers instead.
But thats only my feelings. thx.