Since thieves are the only class currently based on physical means, improvement of endgame possibilities should include physical protection. I propose that a form of damage mitigation be put in play for all thieves that would increase their defensive skill by means of augment and root them in place. The cost would be their current gp. The duration would be their gp/10 in seconds. The bonus would be increased by gp_cost/10 minus the number of seconds that had ticked away.
This is close to the way EQ endgame physical classes work with stamina, but I thought I would throw this out there for the poor thieves to think about.