I know there are those that don't like the new armor proficiencies and it makes sense for the argument that the armor prof should just reduce any negatives associated with wearing heavy armors.  However there is another way to look at these armor profs, and that is as a way to allow for greater depth of gameplay.  By having the different armor profs it allows you to define what type of armor your troops wear and then when the game is released or maybe before modders can create additional armor upgrades so you can have troops with the same type of armor bu still receive upgrades.  Now the catch, without the encumbrance system you still run into the question of why not just put the heaviest armor on each troop and then just mitigate the negatives.  Having both would allow for the best of both worlds for the AI to be able to upgrade their troops and stay competitive, at least more so, with human players while still giving the human players some flexibility to create interesting combinations.