This is possible.
This is violating against privacy, if some users do not want to share their last names. I can understand their mind, and if they don't want they won't share their last playernames.

Paul will be back today/tomorrow, in my eyes we can make it maybe like this:
A user needs to set a setting in their settings which allows a specific user / all users (dont know yet) to view their last 3-5 (dky) transfers.
The user can allow or reject this setting.

So you guys from the clans could then say, set this setting for an hour to allow, we will see your last names, then we can approve your joining otherwise we can not give you any chance to be in our clan.

Don't know if that's a good idea, feedback would be good. Will tell that Paul when he's coming home & will hear his opinion about this.

Regards,