2: Everyone automatically gets Combat Expertise and Power Attack.
These are simply modes anyone can activate, but are slightly changed:
-Combat Expertise has no BAB cap.
-Power Attack also works on light weapons at +1 damage per -1 accuracy.
I like this, but I'd also add the caveat that a one-handed weapon gets +2 damage per -1 to hit. That puts it on par with a two-hander, so the real change for using a shield is just in the base damage plus half your Str mod. One for one makes sense on light weapons since you get two of them.
Now, you just have to decide if you're cool with a longsword and short sword user effectively getting 3:1, or if you want to cap all weapons at 1:1 if using multiple.
It would make TWF worth a damn without sneak attack, so that's a plus. I've no problem with TWF fucking people up, because it costs a lot to do. You need to spend several feats (or 1 feat and an item if you only want two off-hand attacks), have decent Dex (unlike THF, where you can dump everything except Str and rock face), and you take attack penalties on top of it. You also spend twice as much cash to keep your weapons relevant when you already have money problems. In short, TWF needs to either have it's costs brought down
a lot, or it needs to be awesome to make up for it.
As is, the only viable non-sneak attacking (or other bonus damage-stacking) TWF build is a Revenant Blade, and that's only because they get to go 2-for-1 with their double weapon. Another nice thing is that these changes don't make the Revenant Blade obsolete, simply less awesome, which is fine.