I'm sorry if this isn't the place for a non-pod member to chime in; if so please feel free to ignore this and I'll happily go back to observing
After following the discussion here, I thought I'd throw out an alternate idea for Brainjack that carries over some of the "digitize" theme while also opening up some unique gameplay considerations. I realize that this power may be too complicated or unusual for the purpose of this set, but figured it couldn't hurt to share and maybe provide inspiration for Jace's powerset. It would also be kind of a fun homage to Finn from the original master set. I also want to give credit to Ixe for helping me polish this power when I first created it for use on an evil viking spirit hero I made.
Brainjack
Instead of attacking, you may choose any Unique Hero within four clear sight spaces of Jace and place Jace on that figure's Army Card. Brainjack adds 1 to the normal attack number on that card. After taking a turn with Jace, or after revealing an order marker on Jace's card, if Jace is on an Army Card, you may take temporary control of that Hero and immediately take a turn with that Hero. At the end of that turn, control of the Hero reverts to its previous owner and roll the 20-sided die. All order markers that were on that Hero's Army Card will stay on the Army Card. If you roll a 1-10 place Jace adjacent to the brainjacked hero. If you roll an 11 or higher, you may instead choose for Jace to remain on that Army Card. If the brainjacked Hero is destroyed while Jace is on that figure's Army Card, you may place Jace onto any space that figure last occupied.