This is a Horrible idea, there are a few things for consideration here.
Bots/Cheaters Don’t care about rules hence they’re breaking them in the first place so they will just seek a means to by pass this.
Most importantly It’s thee Average player such as you & I that Suffers the most from a “captcha”.
Blizzard is Moving the Game to it’s New Updated system Same as Warcraft reforged which will already Increase the detection and Prevention of Botting/mods/cheating.
Furthermore instead of Punishing thee average player they should Incorporate or Block players that hit on/under a Specified Criteria flagging them for a Captcha and that’s thee Only way I think ppl could ever get behind this if at all. (making it more random and alot less frequent and this could range from making to many games too quickly or your mouse pointer flowing in a straight line. ect ect.