Difference between melee stamina and ranged stamina is 100% purely just the weapon on front bar and the skills of that weapon. Other than that every thing they have - gear, other skills, medium armor passives, .. is same.
Stamina melee builds do generally more dps than ranged magicka builds, stamina ranged builds do generally less dps than ranged magicka.
Therefore your theory and proposition would at best change nothing but arguably it would actually nerf light armor substantially in PVP and marginally in PVE as penetration is far superior damage component and also quite and expensive to get. In PVE meta medium armor builds from the passive in question get just about 3-4 set bonus values while LA pen passive is about 3.3 bonuses. One set bonus of penetration is superior to one set bonus of weapon/spell damage (as long as there is mitigation to penetrate). Cherry on top, many melee (DW) stamina builds in PVE can afford to get necessary amount of penetration just by putting sharpened on one where LA armor users would have to sacrifice full trait to get it with your change and many melee stamina builds in PVP can use maul to get high amounts of penetration and/or use ultimate that gives it all for few secs where LA armor users got nada.