I think the advantage of loyal wingman for AA duties compared to a subsonic bomber is that you can be risker with tactics as the platform is more disposable, i.e high altitude supersonic launch, which will give it good missile performance also.The H-20 will be able to carry much larger cruise missiles than the loyal wingman drones available. Which means it will be able to attack well outside the range of opposing enemy aircraft if required. As for it being expensive to use for aerial refueling, a refueling variant of the H-20 would likely not need any of the expensive weapon systems, bomb bay, and radar as on the bomber variant. So how expensive would it be really?
The refueling variant would only be used for operations close to the front line. I am fairly sure something like the tanker version of the Y-20 would be used further behind the lines. Another possibility would be a tanker variant of the C929 once that comes out. Similar to A330MRTT.
How about the US approach of using UAVs for refueling also? The MQ-25 Stingray comes to mind, it will be far cheaper to operate comparing to a converted stealth bomber.