hafrogman
Adventurer
Well, I had a whole thought train typed out, and then ENWorld lost it on me. *sigh*All this said my personal preference is Option 1 I think if the numbers can be tweaked just right. Whatever is done we should remember to keep it simple to minimize the bookkeeping issues and the like.
Short version: Con is supposed to be important to battleragers, this is part of the cost of the feature as it's a bad deal for a Strength based class. Perhaps the DR could be based on Con.
Heroic: 1/2 Con bonus (DR 1-2)
Paragon: 1 + 1/2 Con bonus (DR 3-4)
Epic: 2 + 1/2 Con bonus (DR 4-6)
Those with better Con have better DR and worse non-fortitude saves.
Changing to DR would require removing or changing the damage bonus requirement as well, per my previous post.