These are some things that might contribute a
bit of the power and flexibility needed (assuming, as it seems you do, that you want to keep other things along a similar-ish power curve):
* High starting scores -- 32+ PB / 5d6 drop 2 / heroic array. . something like that.
* A feat every level.
* An ability score increase every 2 levels (starting at 2nd).
* Degrees of 'masterwork-ness', scaling up from the standard, maybe including some magic-like properties, or at least DR-defeating ones (perhaps gained via 'epic feats' - so to speak - accomplished by the PCs, for instance).
* Completely free multiclassing (i.e., no favoured class or whatever).
* Possibly a supportive variant health/combat system like
Reserve Points or
Damage Conversion, from Unearthed Arcana (or the SRD as, the case may be).
* More emphasis on the Healing skill, with herbalism and stuff tacked on (or a separate subsystem, if preferred).
* Maybe add in
Autohypnosis, as one means of combating a few little potential problems and weaknesses. Class skill for all? Just a thought.
* More skill points per level.
There are lots of other (free) possibilities of course, but these ones jsut came to mind. Hope it's at all helpful.
