The local authorities have indeed shut it down in the past. There has been a police car out there waving taxis through the circle preventing them from stopping. It may not happen all that often but it does happen, mostly, I surmise, when so many people are doing what you are talking about that it causes a traffic problem. You might not want to talk about it too much. What you are advising only works when not many people do it; if everyone did it you'd never get a cab out there.It's less than a hundred yards, there is a sidewalk and if spending a couple minutes in the hot sun bothers you, you probably are vacationing in the wrong place. I suppose the idea of walking with a rolling bag may not interest some folks, but doesn't seem that challenging to me. It's off the airport property and the "local authorities" haven't "shut it down" yet. In fact, I get picked up by the first free cab that goes by every time. I bet I'm at my hotel before the first van leaves.
But do what ever floats yer boat. Personally, I prefer not to be jammed in a van like sardines.

I've already been packed like a sardine in a plane for a couple of hours getting down there, so a few more minutes doesn't bother me at all. I also travel with my wife, three 50# rolling bags, and two carry ons, so it's not a trivial endeavor to hoof it out there. And I have been to Cozumel 30 or 40 times, so I know where I am vacationing and what works for me. As for the time, I am on island time from the moment my bags are checked, so getting to the hotel a few minutes earlier isn't an incentive.
But whatever. It's an option, just not one that I would ever use.
BTW, I just measured it on Google Earth. You are correct, it isn't 100 yards. It's 216 yards.