Grant,
You need to be careful recommending the retro-fitting of weep holes. This one (issue) can cause more damage than possible 'good' when done wrong which, most of the time-- *IS* done wrong.
When ole bubba gets out his drill bit and hammer-drills thru the mortar, it ainn-a stopp'in right'a way

. The problem is when the drill goes thru the sheathing! Once that happens, then moisture is going to come to the *inside* as well.
It's one of these things where you have got to inform the buyer as to what they are getting into and advise them that most of the retro-fitting is usually not done right, then let them know of the ramifications of what can happen without weeps and what they are designed to do when installed properly.
"Identify" and "educate" is my advice.
rr