After studying a lot about how the fence destruction works in the 1.16 patch, I've discovered what is the actual issue in base raiding in dayz.
To undestand it well you need to know that the fence is consisted of three parts, the woden frame, the woden wall and the metal wall, each one of them having their own health.
Respectvily 5g, 7g and 12g (g standing for how many grenades it take to be destroyed)
The problem is exactly how dayz phsics work, the damage dealt by a grenade is an "area damage", so it goes through the wal and afects the frame as well, making both walls be destroyed with 5 grenades, instead of how many it would take to destroy the wall + frame.
To solve that problem I came up with a solution, increasing the fframe health depending on the wall built on it. Basicaly, lets supouse that a wooden wall is built, the frame would have 5g and the wall 7g, to compensate that, the new frame healph value would be the sum of both the old frame healph and the wall healph, in total 12g. So when the players rais this fence with grenades, after the 7th, the wall would colapse, but the frame would be there still, with 5g of healph.
Same works for the metal fence, but with the frame having 17u of healph.
This is just an idea, but in my opinion, the woden fence and the metal fence should have a total healph respectvily of 8g and 12g, in numbers would mean that the frames would have 8g and 12g of healph and the wooden wall and metal wall would have something like 4g and 8g. so both of the fence frames would apear 4g before been destroyed.