Our concern is the foreign convictions themselves may have been wrongfully obtained. There are too many variables. It will make the citizenship application process a lot more costly because it will require more resources to determine which convictions you consider and which you don't.
If you do make that a requirement and require people to disclose, then I can see if someone did not disclose it becomes a misrepresentation issue. I think that overall there are too many variables and too many questionable convictions for us to justify making it a requirement.