Heh, there have been a TON of alternate Toughnesses on these boards over the past few years. It's not quite Harm-level houseruling, but it's close.
One suggestion that I liked involved making a Feat chain, so that you didn't feel so badly about taking a weaker Feat. So, the base Toughness gave +1 HP/level, then Dwarf's Toughness gave the ability to stay conscious while at negative HP, then Giant's Toughness gave DR, then Dragon's Toughness gave something nice I can't remember.
The problem is, you really start overlapping into Barbarian territory if you do this; a Fighter with +1 HP/level is just a fighter with a d12 HD, and if you start letting him get DR, why play a Barbarian?