We already allow trades on the WBO. Yours is an interesting idea, but harder to execute correctly. You're placing extra work on your dad to hunt for packages. As I've mentioned I'm a bit of a knife collector. Some of the pieces I've handled cost in the $400-700 range. So people take extra precautions when conducting trades/loans. People will generally be apprehensive on trading unless there are a few things taken care of.
-Insured shipping is a must
-User usually would have some sort of reputation of the forum. Credibility is a huge thing
-some repercussions if one party fails to uphold their end of the bargain.
These are sort of the unwritten rules on most forums. The problem is that with Beyblades most are inexpensive, so insured shipping, especially international would be more expensive than the top itself. I'm not sure if your system is necessarily practical over what's already allowed. Generally I feel trading beys should be left with people that you know you can trust and rare tops. I've seen far too many scams/horror stories with really expensive items.
Thanks to Kai-V for the avatar and signature!