1.Armor does not suffer from diminishing returns.
2.Armor reduces damage before anything else is applied, like crit mod or resistance penetration.
3.Armor protects you from Weapon damage, which scales very high for NPCs due to the physical power from Weapon Training talents, and is therefore the most dangerous.
4.While not all Weapon damage is necessarily Physical, most of it is, and Physical resistance is much harder to come by than other types.
5.The 'downsides' of Armor are negligible (i.e. Fatigue and Encumbrance).
6. The 'requirements' for armor and armor training are also negligible, as they can be met by swapping in +STR gear.
What I would like to see are some ideas that make Heavy, Light and Cloth more appealing for certain classes without nerfing Massive.
Here's an example:
With my Naloren add on, I attempted to make Heavy(Mail) appealing to Naloren characters because it fits into their lore. They have a racial talent which grants them a bonus to movement and attack speed and a chance to completely ignore damage while wearing Heavy. The last point in the talent (it's tied to the last point mostly to keep it optional) will change the requirement for wearing Heavy from Strength to Constitution. This last bit was an attempt to make it a little more appealing for non-Weapon-damage classes who would be stacking Strength only for armor. However, the usefulness of Con is still quite debatable, and the requirement for the Armor Training talent remains Strength, so I think I missed the mark a bit on that one, in retrospect.
Tweaks along these lines are the kinds of things I would like to see. Something that makes other armor types more appealing, while not making them so powerful that they become the obvious choice, either.
I'll kick it off with a couple of ideas I had.
One would be a 'Mystic Armor' talent for 'Caster' type classes (Mage, Necro, Summoner, Doomed, Corrupter, etc) that would grant certain bonuses for wearing Cloth armor and require (Willpower?) to invest in. Minor increases to Spell/Mind speed and movement speed (scaling on something like 5%-15%) are the first thing to come to mind. This would make staying at range and avoiding projectiles a bit easier by making movement and the things you do offensively take less turn energy. Without some type of damage mitigation, though, I'm not sure if this would be enough to make it an appealing alternative to Massive or not.
So, the other thing that came to mind would be a kind of 'reactive shield' effect that would be triggered by X (Weapon or Physical? I'm not sure which would be better) damage above a certain percent of your max life. The effect would convert a percent of the triggering damage (and possibly all damage for the rest of that turn) into 'resource' damage, such that it would drain an amount of Mana/Pos/Neg/Vim/etc based on the percent of max life the damage would equate to. Quick example: If you had 1000 life and you were hit for 400 damage, the effect would trigger and the damage would be reduced by some percent (say 25% for this example). You would take 300 damage to your health and the remainder would drain resources based on the ratio of negated damage to your max life, in this case 10%. I don't know if that should be a direct scale (i.e. it would drain 10% of your max resource) or a proportional scale (such that 10% max life worth of negated damage would drain 5% percent of your resources, if it were a 50% proportional scale).
Obvious problems here:
Wilder and Chrono 'caster' classes (Summoner, Ooze, PM) don't have a 'max' resource, so it would make these calculations impossible and an alternative hard to balance. It could be tied to fail chance instead, or a portion of their fail threshold, maybe?
Anno and Doomed have odd resource management already with Hate and Pos/Neg, so I'm not sure how this would work out for them.
I have some ideas for Light, too, but I'd like to see what other folks think before I invest a load of thought and time into this.
Maybe everyone else is fine with an Archer running around in Massive armor, but it irks me to no end

If there are enough folks who agree, though, and we can generate some good ideas here, I would be up for putting in the time to craft an add on for this (as I think that Armor is so ingrained into standard ToME play that making changes to the base game at this point would take way, way more balancing than I have the time for, not to mention more knowledge of the engine than I posses).
So, what does everyone think? Am I right about the advantages of Massive, and does it bother anyone else?