First off, a disclaimer to say this isn't directly in response to anyone, but to the notion of making up our own definition of words that already exist is okay. I see it happen on sites of all sorts, and it never fails to annoy me.
Wouldn't it be great if we could all just make arbitrary meanings for words already in the dictionary?? For instance, my definition of frontal lobotomy means "sexual encounter." I think that's pretty sweet.
Therefore, if I tell you I hope you have a frontal lobotomy this weekend, I hope you take it to heart and go out, wear the hat and blow those cheesy whistles they hand out for New Year's and have the best frontal lobotomy of your life.
The word "ace," contrary to your or my own personal definition, is already in the dictionary. It simply means the best pitcher on a baseball team's pitching staff. I wrote the good people at Merriam Webster to ask if they might add the word "starting" in there to differentiate between the rotation and the bullpen, but they haven't gotten back to me on whether that will go through or not.
I'd like to present that there are not just five or six or eight or 12 aces per league, but 16 in the NL and 14 in the AL, whether you like it or not.
In the future, let's go ahead and use the term properly, now that we all know that there is, in fact, a clear definition of the term.
Personally, I don't care whether you say a team has multiple #1s or such, though there technically can only be one #1 and multiple #1s are the main reason numerals such as two and three were thought into existence. But at least I can get what you're saying contextually in such circumstances.
Fortunately, the good folks at Merriam Webster have as yet to define #1 as a team's best pitcher. I propose that the term "#1" means a pitcher that could be the best pitcher on many teams (it needn't be unanimous, but let's say at least 30%, or 9 teams) in the league.
This number, I feel, allows the term to breathe a little bit and prevents elitist exclusion of pitchers that are extraordinarily adept at their trade. Feel free to make your definition of #1 to be 15 or 18 or any number of teams you want (the more teams, the more elitist). This term is still in its infancy, according to our pals at Merriam Webster, so it's okay to fiddle around with it as you like!!
Thanks to everyone for their consideration on this matter,