They have offered to have their passports certified for identification purposes.
That's really big of them, but if you are willing to do what they ask, they should at least offer to bear your children.
Banking a foreign national who is sitting across the desk from you is one thing. It requires some expertise and a certain appetite for risk. Opening an account that you expect to have a zero balance for a foreign national you have never seen, will never see, just because a third party wants you to is just bad judgment. (N.B. Once the account is open, it is open for all other types of activity, not just deposits from a source your bank regards as credible.)
Probably the quickest way to kill this idea is to point to the requirements the new due diligence regulation would impose and the fact that some percentage of these customers would be classified as "higher risk"; i.e. getting a passport is a drop in the bucket.
P.S. Curiosity only, what in the devil does it mean to "certify" a passport? I ask the question only to open the door to saying, I don't think it means anything at all.