For Learning Heroes, we have Wendy who hits 58 on robotics, wasabi who hits 44 on Optics and Energy, Alan who has 43 in programming (48 in security), and Janus (who is currently unailable) hitting 44 on both Genetics and Vehicles. We are not hurting for Heroes who can tackle high-DC Learning nationals.
You know what your premise is missing? A quest Leader. None of the units you've listed are suitable to leading a quest (even the one that doesn't currently exist) So you'd have to either make room for the Black Ops Heroball anyways, or send (the currently unavailable) Coyote. In either case, Learning problem taken care of.
And if for some reason you didn't want to have one of our Quest Leader units on this? Send Norm for Martial, and Mez for Learning. Or heck, send Gomez! The primary reason we'd want Learning on a qiest to the Boiling Isles is Bellos' magitech, and that's his specialty!
In either case, our quests benefit a lot more for having a strong Leadership unit than for having an extra floater. Not to mention the importance to Martial nationals, the field we actually created the Heroball to fix, because all the DCs are so high.
Sabotaging the Heroballs' primary purpose with Gomez' single-digit Martial to keep one Unit as a Floater makes no sense.
And what if we have a high DC action that isn't someones specialty, like Greco-Roman Terraforming or Insect Control? Like, your taking this as a Lizzy vs Gomex, i'm telling you your understanding of Flex units is wrong!
A Heroball does not make someone a better flex unit, it does the opposite! Stats aren't the only thing that makes a good flex unit! A Flex unit is someone who can be easily slotted in when needed. YOU FUNDAMENTALLY CAN NOT DO THAT WITH A HEROBALL! They take 3 slots, which means you have 2 characters left. The characters chosen for the Dec Quest where because they would be important narratively and mechanically. If we were just minmaxing, we would solely focus on characters that are statistically appropriate for quest, not thematically. A Quest leader and then one of every other stat. Monogram is not good statistically for quest, at all, but he should absolutely be on that quest. Russ and Janna are better statwise, but also have thematic reasons to be there. Lizzy lets us get away with that stuff, and she doesn't need stupidly high stats to do so.
Like god, the amount of "But it raises her stats" your doing ignores that Lizzy's great stats are only part of why it works for her. She has good independent martial so if she gets attacked she's fine, unlike Gomez, which is important when doing quest in dangerous locals. She has no Specialty Bonus like the Specialist you listed so she is just universally good at learning, which is important if were tackling something that we lack a specialist for. Her disposition means unless something on the quest or in the interlude happens, she won't get angry about being made to do that. Lizzy is a good Flex unit since she has strong stats, she can do anything without major commitment. Doofquest is not just a raw numbers game, and Lizzy helps us be thematic without sacrificing 2 highly important stats on Quest, and lets us tackle Learning DCs for things without specialist. Thats Lizzy's power, being just able to do lots of things when we need them done without sacrificing much else.
Onto Gomez vs Lizzy, the thing shouldn't be "It makes Lizzy a better Flex" its "Do we value a Versatile Ball, or a Specialized One". Lizzy will give the ball a lot more martial oomph, which if we just want em to do Black Ops, is fine. Gomez gives it a decently sized "Occult" score, and the ability to possibly summon a Divinos in enemy territory. It also will make Gomez far easier to manage since without direct supervision he is kind of losing it as his personnel shows. Lizzy doesn't really fit in terms of her personal narrative unlike Gomez, she has her friend group already, and this would take her from them so she likely won't give her full stat boost.