For you people who think it is hard to manipulate the thumb safety on a Shield, order some talon grips and cut off a tiny square on the left side (if you are right handed, being the least used portion of the grip) then apply that little square to the safety.
Now you have a high friction tab on your safety that doesn't stick out and interfere with a conceal holster.
Sounds like a reasonable plan to me.
Ultimately, I wish an aftermarket company (are you listening Apex?) would make us a Shield safety that resembles the standard unit on the FS M&Ps.