Attempting to be universally accepted is exactly what makes this proposed open letter lack conviction. Also, it's not like something has to be unanimously loved to make an impact.
Because by the time you filter out the contested opinions all that is left is obvious suggestions and trivial requests. An open letter is a poor vehicle to get the developers attention for so little. They are either already adressing it or have their own separate priorities. It's just repetition for them, minus the constructive specifics they'll get looking at the mods.
Ok, lets first start at a place where we both agree:
We want to see the next Smash Brothers game improved, in general polish, fun, and in competitiveness.
Now lets try to be
constructive to this common goal. Something more than just "this idea is bad and won't work," but actual ways to make this shared dream real.
If you believe the ideas presented so far all either 1)contested, 2)obvious, or 3)trivial, then I challenge you to come up with better ones. Here are just two ideas already presented that I believe are not contested, obvious, or trivial:
-give a game option to make items appear only after they display where they will appear for a few seconds. Would this really be contested as its an option to turn on or off? Its not obvious, otherwise it would have been in Melee/Brawl. And its not trivial because it makes competitively using items possible.
-preload transformation characters. Who would contest this? If its obvious, then why didn't Brawl have it? Its not trivial because it makes playing characters like PT and sheik/zelda very different.
If you believe that an open letter is a bad way to present these ideas, I challenge you to come up with a better way to present them. Do you think a video presentation could be effective? How about someone trying to talk to the development team at a conference?
Saying that the Brawl mods are the most effective constructive criticism doesn't mean that we can't try to influence the next Smash in other ways.