You're misinterpreting what I'm saying, Gian.
The target won't maintain a set position in regards to your plane, it will maintain a set position PERIOD.
Let's say you're in the TA flying along. You type in the text bar .target static
This "drops" the target at your location, becoming a static object with a range icon like an enemy aircraft (so range beyond 1000yds measured in 500yd intervals, and 200yd intervals under 1000yds. You can fly away from it, towards it, around it, over it, or under it. The target ALWAYS faces towards you so you have a flat face at which to aim, but the target itself stays in one fixed position on the map.
This is different than what you were asking, in which the target was to always remain centered on your gunsight.
This would be INVALUABLE as a training tool both for general accuracy and to determine if you're firing inside convergence.
We'd also need something like: .target show so you can review your hit pattern more easily.