Oupa,
Sadly it is not that simple.
In order for these lengthened pins to work they would have to perfectly fill the striker hole.
This means that they would have to be flush with the nipple which also means they would have to have flat tips with sharp corners and this in itself is bad news regarding the possability of piercing the cup as well as other issues.
If a spherical tip was used the cup metal could still flow into the outer part of the nipple drilling.
Reducing the diameter of the strikers is no big deal on guns with bushed pins.
By the way, cartridges developing low pressures like many of the old Nitro Express rounds, often still work well with larger diameter strikers.
The problem concerning flow back of cup metal into the striker hole is usually associated with higher pressures like those developed by the 375 mag and others.