The only problem I see with this is most everyone out there like RetroCDN and Archive.org is simply pinching everyone else's scans so I'm not sure what value there is pointing to other sites? If it's to allow scanning members to determine which mags don't need to be scanned because someone else has already done it that is fraught with peril in several ways...
Existing scan may be missing pages/ centre posters etc.
Quality of the other sites scans might be inconsistent with your requirements
Other sites may have just ripped your scans off anyway but also may have edited them ( to remove Retromags advertising page and/or dropped quality )
I should think it would be far better to concentrate on the scans from members of this site? The only sites you can verify that most files originated from are OoPA, mine and Retromags. Pointing to Archive.org for most gaming magazine files hosted there is like advertising/popularizing a thief in my opinion.