Ways to make white-box cryptography AES implementation more difficult to be broken
Is the above way reasonable (if we cannot find a proper implementation)?


No, there are currently no such code-obfuscation algorithms that securely obfuscate code to a point where it's very hard to reverse engineer it.


  Please recommend any mature WBC implementations (not broken yet)


I'm not aware of any WBC implementations for AES.

Note, that a successful implementation of a WB-AES algorithm would mean that the "one-wayness" (very hard to invert) would turn this algorithm into a public-key-cryptosystem without a need for asymmetric cryptography (you would just publish the WBC-AES-implementation and the key wouldn't leak). So I'm pretty sure that there are no unbroken implementations.

It could be that there are some unbroken WBC implementations out there, but I don't think that they would remain unbroken for long if they would attract a lot of attention from the cryptographic community.


  Any other better idea? (other than re-design &amp; evaluate a new WBC algorithm)


No. As Geoffroy Couteau and I commented, self-made code obfuscation is likely unsecure for many reasons, the main reason being that the security would rely on the fact that nobody ever would gain knowledge of your obfuscation algorithm.