One the one hand, yes the action system and balance of PF2e would be better for Larian. There's even natural in-game ways to get extra and reduce your opponent's actions, something Larian has homebrewed into BG3. On the other hand, PF2e has MUCH tighter math than 5e, and Larian's desire to homebrew things would seriously mess with that.
Larian also almost certainly wouldn't have chosen that system. They likely went for D&D5e/BG3 because of the brand-name recognition, which pathfinder certainly doesn't have. And if they somehow had chosen a pathfinder game, the revenue and thus budget and thus scope would have likely been much smaller...
Doesn't have to be Baldur's Gate title to be successful. Look at Owlcat studio and their two games. Although shame they also never switched to second edition, and preferred switching IP entirely.
PF2e actually easier to understand and reverse engineer, if you dive deep into. So homebrewing, might not be super easy, but certainly possible. And unlike with 5e, you actually can preserve the balance, instead of broken even further already quite "shoddy" system.
