How can I add more rounds to AES?
The AES key schedule isn't more secure than using PBKDF2 on the data -- but it is a lot faster, and requires many fewer gates in silicon.  Performance is important.

As far as devising your own variant of AES, with more rounds: don't do that.  There's no good reason to do that (it is exceptionally unlikely that AES is the weakest link in your system), and you can easily introduce subtle security vulnerabilities.  Whatever problem you have that you think motivates this, modifying AES isn't the solution.