Chris I don't think it would hurt but could even help a tiny bit.
You just need to COACH HIM and be sure he coaches anyone that could answer the phone how to handle Google moderation calls.
AND REALLY NEED TO WARN HIM that if he shows address EVEN IF he has an office there is a very good chance he's going to get his listing deleted. THOUSANDS (I truly think hundreds of thousands) of listings were deleted and some have been down for 2 months.
Sometimes they DON'T do moderation calls, they just delete.
And as you know locksmiths are tricky anyway.
If it were me personally, no way in hell knowing all I know, would I risk my listing just to show address so people could drop off keys. Most would call 1st then you can give address and most would click to check out site, put address there. But I would NOT risk changing Place page address if already hidden.