I'm guessing the 3-pointer potential would have been related to that.
In Shugo Chara canon, Amu already was the equivalent of a "Wildcard" by Chara user standards on account of having multiple Charas, which was why she was given the title "Joker" among the Guardians (which I think I mentioned somewhere before).
Assuming the Sea of Souls and Road of Stars are seemingly the same thing here, my current speculation is that Baughn called her a "low-budget" Wildcard because she uses Charas and not actual Personas and Charas are "low-budget" Personas that usually disappear after a few years. Unless there's something unrevealed in this quest, she also doesn't have proper Social Links or Velvet Room support, which is what a regular Wildcard would have. The closest thing she might have to that is being able to Chara Transform with other people's Charas. She can access the Road of Stars through Dia, but until she channeled that Persona/demon earlier, she never summoned anything other than her own Charas from it either.
Even though it is effectively what the stunt is proposing, it's an absolute hail mary stretch to think she could reach into the Sea of Souls and try to form/leverage impromptu knock-off Social Links with a whole bunch of random souls that she may not ever have met before, or spoken more than a single sentence to if they were a classmate. The kind of stretch that relies not just on the assumption that the Sea of Souls and the Road of Stars are the same, but that any form of "Social Links" are something she can actually do and not completely out of budget for her (as canonically, there's no Shugo Chara equivalent).
There are multiple ways I could try to justify this. Some of the possible rationales are:
1. She just summoned a Persona to heal Saaya. If you assume it was a Persona, by extension that means she could be graduating from Chara-using Wildcard to Persona-using Wildcard. Which means it may be possible to form Social Links (leaving aside that real Wildcards take months to develop them properly).
2. She always could, already has and just never noticed she had Social Links because she doesn't have a Velvet Room attendant to tell her when she's forged them. She secretly has max rank Links with all the ex-Guardians, half the current Guardians and maybe some of her old friends.
3. She hasn't formed any yet, but will in possible futures and since these "bonds that never break" exist in the Sea of Souls, given it is actually the same thing as the Road of Stars, they are bonds that exist outside space and time. Meaning that future bonds are accessible even to past selves that haven't yet formed them.
4. They're not Social Links. She's borrowing what she thinks of as other people's Heart's Eggs. She was able to meet some she previously met the last time she went to the Road of Stars. Everybody has one and she can Chara Transform with other people's. She's just going to be borrowing a whole lot of other people's at once. Borrowing Heart's Eggs is considered a "low-budget" version of Social Links.
Take your pick.
As the one who wrote the stunt, I personally regard every single one of these as bullshit, even as I argue there's some tiny minute chance they may be possible.
Fortunately, what I personally think also doesn't matter, as I'm not the one grading the worth of the stunts.