And that's really the point, isn't it? When you look at the contenders that have a REALLY strong 1-2 punch...
Houston - added Verlander from outside.
Washington - added Scherzer from outside.
Boston - added BOTH Sale and Price from outside.
Yankees - added Tanaka (and Gray and possibly Cole) from outside.
Cleveland - Kluber came from outside.
Cubs - added Lester (and Arrieta when they had him for that matter) from outside.
Arizona - added both Greinke and Ray from outside.
Dodgers - don't really have that #2 that stops you in your tracks to pair with Kershaw (although Buehler could turn into that guy).
The only team that has two guys on that list that were developed in their own organization is the Mutts - and it's easy to point out that Syndergaard came from outside even though he finished developing in their system.
Houston - added Verlander from outside.
Verlander was a salary dump from Detroit at a time when the Astros were clearly competitive for a WS. He didn't cost much in relative terms.
Washington - added Scherzer from outside.
FA signing. No talent went the other way.
Boston - added BOTH Sale and Price from outside.
Price was a FA. Sale was costly in terms of talent and is an example of what the Braves would have to give up. Boston can afford to do that. The Braves can't.
Yankees - added Tanaka (and Gray and possibly Cole) from outside.
Tanaka signed as a FA. Gray is a reputation guy that hasn't pitched really well since 2015 and is also an injury risk. He doesn't belong on the list and what the Yankees traded for him shows it.
Cleveland - Kluber came from outside.
Minor league acquisition through trade. Not equivalent to what is discussed - trading for an established TOR starter.
Cubs - added Lester (and Arrieta when they had him for that matter) from outside.
Lester was a FA signing. Arrieta was a nothing until Chicago turned him around.
Arizona - added both Greinke and Ray from outside.
Greinke was a FA signing. Ray was an unknown traded twice before ending with Arizona. Was part of a three team trade with Green going to the Tigers and Gregorius going to the Yanks.
Dodgers - don't really have that #2 that stops you in your tracks to pair with Kershaw (although Buehler could turn into that guy).
All internal unless you count Wood who was a Brave.
So essentially what you have is
one situation that is equivalent to what people are advocating the Braves do and that was the Sale acquisition by Boston where Boston sent the top prospect in baseball that cost them $63M to sign (Moncada), one of the top power RH starters in the game (Kopech), a useful and projectable prospect outfielder (Basabe) and a live arm (Diaz). So essentially equivalent to a trade where the Braves send Acuna, Wright, Waters and Sanchez.
When looked at that way it isn't so desirable anymore.
People want the Unicorn to show up where the Braves get a TOR guy for nothing that will be missed. It would take a very special set of circumstances for that to happen. One way would be if the team trading the player had other really bad contracts that they wanted to move AND the Braves had the payroll space to eat that money. Other than that, you would be trading away from the rebuild, robbing from tomorrow for the short term of today.
It would be unwise IMO, BUT, if you absolutely HAVE to have a guy, go sign a FA. That makes much more sense than trading for an Archer or equivalent.