I invited the old pilot of the earlier version SimplePlanes back, and,
make the transparent cockpit exact the same size shape of the default cockpit, so that, you could take this cockpit away save as assembly and replace the cockpit of any planes, just as this snapshot

Besides the glass transparent cockpit, I added a target lock on overlay like HMD, press c to change to viewer 1 in the cockpit, press r to enable radar to air mode, now, you can press F9 to turn off the original flight instrument of simpleplanes, you can find a rectangle move with the selected target:

Video here:

The example plane here
Pigpen-With-Real-Glass-V-0-1-5

why it is not very accurate?

because I didn't take the roll angle of myself into the calculation, so, next version, I will make it, also, I will try to design a way to show the distance, in the final, any modifications of this model are appreciated!