I plan to make several changes during Winter break:
Code: will use class instead of functions. Clean up messy codes, make it easier for you to make changes if needed.

On admin side:
1. No need to add new field for each product id/model. All will be in the same input field, separated by comma or semicolon. I realize from my own experience that this will make the job even faster and easier.
2. No longer list all cross-sells by default to speed up the loading (especially if you have lots of xsells)
3. Easy retrieval: If you have a group of xsell products (A, B, C) and want to add D to this group, you will be able to do this very easily.
The same with master product (1 way cross sell)

On catalog side:
Will merge the original XSell to the package to make it easier for you.

Let me know if there is anything else you want.