Well im sorry to tell you this but X1 and X2 are both "hide and never get shot games" the point of shields isn't to make your units tanky but to give infantry a buffer, a "get out of jail free" card so to speak.
The point of tactics games is to minimize the amount of incoming and maximize the outgoing damage and a 80hp buffer is massive. This means that shield units can take 1-2 hits scot free and is huge in the long run as a limiting factor even mid game to sortie rates is units getting wounded. If anything making shield into armor is a nerf as this guarantees that shields would take damage and in that case why not just bring a 2h gun and "hide and never get shot". The fact that as it stands shields act as a second hit point pool means I can comfortably get the shield in close knowing they can take 1 hit and deploy smokes/stuns so the squad can follow up is invaluable even if they lose the shield on that sortie as if they take no damage I still then follow up with a squad to the next drop.
While I understand the benefits of extra armor it would arguably do the same job if not worse, that is unless it we to give such a large amount as to completely necessitate the rebalancing of the game.
As it stands the current "buffer" model fulfills the design goal, an "armor" based tank that is effective would probably either be worse or overpowered as you would able to face tank and heal several hits.
Overall i think that this model has great potential but im not sure if it fits into the current framework of the game and if anything would feel less realistic.