Again, and I don't know how many times I will have to say this...it is a misconception that 3.5 does not have rules support for these things. Plain and simple, yes or no question and the answer is yes.
But, existence is - plain and simple - not enough. It has to work. Does it?
My answer would be no. You have to change a lot more in the system then just add some UA rules to make things work. To learn more skills, the DM might allow the Skill Knowledge feat.
But wait - why can this just be a single feat that nets me an extra skill points equal to 3+level? How is this balanced with the core rules, where what the best feats do is add +2 to two skills, +3 to one skill, +4 to a conditional use of the skill, or add 4 skill ranks? Did the guys with the last feat screw up?
Wouldn't this system mean that Fighter suddenly become some of the most skillfull characters, while their skills used to suck beforehand?
Most of these ideas are half-baked. They provide a starting point, but they haven't been tested and they do not necessarily guarantee the same "balance" in the system.
Maybe that's okay if you don't care about balance, just about the way you resolve certain things. But I certainly do not. I want a good way to resolve things and keep a sensible balance between characters (and monsters).
I don't feel that a particular mechanic is supported if not only I have to buy a book (that's okay for me), but also have to work out all the side effects of the change. Adding a new class, feat or spell is far easier then changing the entire way how you resolve a game element.
Heck, doesn't Unearthed Arcana introduce also a "3d6" D&D? Did they ever go through the detailed implications of such changes? It's not just that critical might become more seldom - DC changes and modifiers have an entirely different effect, since you have a different probability curve for your numbers.