I was wondering the same thing as D-naras, but I'm afraid that your post didn't answer my (unspoken) question. To say it myself...
I like where you're going with this (it reminds me of Seerow's Revised Weapons rules), but I don't see how to determine the damage of a newly created weapon. I may have missed it, but I'm beginning to think that the answer isn't in your original post.
EDIT:
Oh! I forgot, but I wanted to address this:
(Emphasis mine.)
This makes me think of the sugliin (2d8, 20/x2 | Frostburn, p77). As the book says, "This weapon is so unwieldy and heavy that making a single attack with it is a full-round action." There is some good news, however; "The Sugliin Mastery feat (see page 50) allows a character to make attacks with this massive weapon normally."
So, there's actually precedence for a "Really Exotic Weapon" that takes two separate, weapon-specific feats to utilize properly.