Kevlar kit: +15HP/20armor/Resist AP20% standard issue kevlar protection
I think you better change all resistances by 15%-25% or so instead of adding HP. That will serve the same purpose, but you will not face increaced wound recovery time, problems after removing armor from a wounded soldier in geoscape. Also armor should not (IMHO) increace time the soldier takes to bleed to death (in case of fatal wound).
All in all the mod seems to make game a lot easier, the game also has its own "class" system - the initial stats of the soldier. If someday programmers will make possible adding more types of soldiers to the game via mods that will be a great breakthrough toward class system.
Even in vanilla its quite easy to get soldiers who have more than 100% aimed shot accuracy with rocket launcher and sometimes rifle, with sniper kits almost 30% of rookies will be too accurate.
he problem with this is not being able to identify classes on battlescape
I used uniforms mod
https://www.openxcom.com/mod/combat-uniform-armors to give my soldiers uniforms of different color according to their role on the battlefield, so that my snipers were always green (jungle armor variants), medics were white (arctic) and so on