Anybody ever had Leupold put new lense coatings on an old, uncoated scope?

Yes, I know I can call Leupold and ask. I disdain being on hold for 16 minutes.

I've never heard of them doing that. Neither have I heard that Leupold ever made uncoated scopes. What I think you are asking is if you can get an old M8 fully multicoated, right ?
You might consider selling it and buying a new fixed magnification scope. E

I've had Leupold replace lenses under warranty free of charge, but I do not think what you want is an option. Send an email so you don't have to wait on the phone.......

I was told by Leupold Canada that they would replace the lenses with current lenses in order to accomplish the coating upgrade. IIRC, they wanted around $200-250 to update a FXIII to FX3 coating specs for me.

I think this was my point. Replace the lenses, yes; put coatings on old lenses (recoat), no. I can think of better ways to spend $200-250 than to update the lenses on a M8 or FX-III........YMMV

Sent back a MC4 M8 6x42 with an oily film on the edge of the front objective lens with instructions to clean interior and upgrade however they could under warranty. I got it back with a work order that said they replaced the erector system for more adjustment and also replaced the front lens with a new one (VXIII). So I guess that's one way to do it. Of course.....no cost to me.