Dont know if this is something other people already figured out or not and I'm not even a super hiveswap person, but this is something that I realized with total clarity today and wanted to write it down in case I'm the first. so i can be vindicated when its shown as true
im not 100% on board but im listening....

Here's what we know:
-The shots of Fiamet's room in Act 3 we've been shown have her with an Earth globe and her cocoon is on top of a human bed. She has definitely been exposed to human culture and lifestyle.
-Grandpa Harley's mansion, conversely, contains an Alternia globe. It's suggested pretty heavily that Grandpa Jake has used the portal to go to Alternia and do big game hunter adventurer shit as you'd expect from him
-Joey, obvs, is one of Jake's many children he abandoned and she is the main character and it's her story
-In Hussie's Hiveswap planning notes (which also contain Fiamet, she's a foundational character for this story) it mentions that Joey wishes she had a sister
Idk I think the writing is on the wall here! I'd be pretty shocked if this wasn't the main thrust of the plot.
(The recent reveal that limebloods were pyrokinetics, which figures into the lime Fiamet's green-fire-breathing axolotl lusus, could maybe connect in some convoluted way to Jake's eventual acquiring of Bec who has green fire First Guardian powers... but that's a bigger question)
i completely forgot some of the act 3 teaser stuff somehow (i may have just focused in on yay yippie axolotl wahoo and forgot everything else ever) okay yah im understanding

I actually never thought about this, but it seems very plausible, the theory I had about the realtionship Jake has with Alternia is very different haha
I basically though Jake's wife was Mindfang on a disguise similar to HIC, because we never know how she dies and how the portal has cherub theming, I saw very plausible it was all Doc Scratch shenanigans or something...
But I like your theory more...
I bet there WILL be some more complicated circumstances around Jake/the portal/Scratch/etc. maybe even more complicated circumstances around Fiamet's birth. But those are harder to guess at.