Im concerned about the Pod working on Foretress decks. There are a few unmade rulings regarding that card, most notibly Blastoise SW.
I am quite certain that if you attach 2 or more energies to Foretress, it will only count towards one flip, just like if you attached one.
This is assumed based on the dawn stadium ruling, which like Foretress, if you attach 3 water energies to a Piplup with 40 damage, you only get to heal 10. This is because you are attaching the energies in a group, or 'together'. When the card says once during your turn, rather than for each energy you attach etc. This is also similar to a Gastrodon ruling where you can move 3 damage counters to the other Gastrodon even if it has only 20 HP left, since you are moving it as 'one'.
You can still attach normally for a flip.
Remember if you have three Foretress out, this means you can still attach a water energy to each one with Blasotise's power, to get three flips, you just can't get flips by attaching to one Foretress.
So, if I have a Blastoise out, and three Foretress, and 10 energies in my hand, I can attach normally, then use Blastoises pwoer for a total of four flips. So if you can get this set up consistantly, Blastoise may still be a considerable theme to use.
This is by no means official, but I am quite confident on this ruling.