I don't own RM titles, so I can't tell wether what I propose now is similar to it - I used to play RM, though, and you do have a point: The interaction of weapon and armor was very nice.
The modifier version is what they do in Martial Law (rigid leather is default, all else give more (or less) stun/ bleeding/ hits). I find that tedious to remember, though, and not very flexible.
I started thinking about a table, but realized: It's not possible to squeeze this option in without ending up with something so similar to RM that it wouldn't make sense to switch systems altogether.
We have 3 things to think about in Harp: Weapon Size, Hit Location and Armor.
Every critical table needs to have roll result by row. So, by column, we can put in one of the said options: hit location (as is done in Martial Law), weapon size (as in Hack n Slash) or armor, as you wish for.
If we want several of these in one combat system, we either need to come up with a solution that doesn't need a table, or accept another table dimension (as in Rolemaster).
E.g., you could have a single table for "Tiny Crush". That way, armor could go into the columns, and hit location would be solved via modifiers (as in HnS).
So, you could have a single table for "Crush on Hand", with either armor or hit-location in the column, or "Crush vs. Chain", with either weapon size or hit location in the column. The remaining option in each example would have to be solved by modifier.
Else, we need cubic tables.
I believe ICE thought this through, and found Armor Adjustment to be the least important thing, so they left it out. Somehow, it's true, because armor affects the attack anyway (by DB), and weapon size and hit location have been highlighted in HnS and Martial Law.
Phew. Does any of this make sense?
