but: all your layers of encryption are AES and AES is broken.
there is no practiacal attac but still, if beeing paranoid than do it right:
My way would be to use the built in encryption, and than encrypt it with true crypt using a cascade of all supportet algorithms. (after checking the whole code for backdoors...)
If you wanna go to that level of paranoia, I suggest that you wrap your wallet encrypted data within a bigger file, containing:
a header
a random number of random bytes
the encrypted wallet data
a random number of random bytes
a footer
In the header, you can put, for example, the offset to find the wallet data first byte.
And in the footer, for example, the wallet data size.
Of course, you can be even more imaginative...
Embed your encrypted data in a .wav file, using
http://naudio.codeplex.com/ (open source) lib, for example, and rename the final file produced "white_noise.wav".
