There is a saying in Turkish;
Even with a golden saddle a donkey is a donkey.
So, no matter what you do to a F16 plane it’s RCS is not going to be improved to a level whereby it can compete with a modern stealthy 5th generation jet. Nor will it have a stealthy airframe like the delta wing planes such as Rafale and Typhoons.
Also remember that, F16, carrying conformal fuel tanks, missiles and various guided ammunitions under its pylons will be compromised further as far as RCS is concerned.
Have Glass version V , actually improves the f16 RCS from 4-5m2 to close to 1m2. With the MMRCA version of F16 they have improved the air inlet duct to lower the plane’s RCS further, and managed below 0.9m2 value. .
Where as a Have Glass-V plane can be detected at 60Nm, the same untreated version can be detected at 90Nm distance according to tests carried out.
But the minute you start adding missiles and tanks on to the airframe, you are taking a back step
But if we are going to use our F16s until 2040s, we need to look in to every little bit of advantage we can gain by improving the paint, air duct, airframe, carry missiles with stealthy geometries etc.