I absolutely love this idea. I don't love going back to movement being an action instead of its own type of resource like in 5e, but I think the flexibility this allows is well worth the trade-off. There are just so many possibilities. With only a weapon, a shield, and movement, you get seven possible combinations of actions on your turn:
3 movements
2 movements, 1 attack
2 movements, raise shield
1 movement, 1 attack, raise shield
1 movement, 2 attacks
2 attacks, raise shield
3 attacks
And it only increases from there the more possible actions you can choose from. Throw in the possibility of drawing a potion from your pack and drinking it, or casting a spell, or trying to intimidate your opponents. There's just so much flexibility, I love it!
What I like most about this approach though, is the possibility of spells and maneuvers that get stronger the more actions you spend on them. Like the example in the first blog post, where each action you spend on Magic Missile gives you an extra missile. Or in the podcast, where they talked about the heal spell healing one target you touch with one action, one target within 30 feet with two actions, or each target within 30 feet with three actions. That's a really, really cool way to give spells and maneuvers some variability, and it makes for a lot of interesting decisions to be made every turn in exploration mode.
Reactions are really cool too. I love them in 5e, but I do sometimes feel they are a little under-utilized Part of the reason Polearm Master is such a good Feat is because it allows you to maximize your action economy by giving you a reliable way to use your Bonus Action and your Reaction every turn. I get the impression that PF2 is going to make better use of the design space Reactions open up. I love that raising your shield is an action, and that doing so not only gives you the option to use your Reaction to block some damage with your shield in response to an attack hitting you. And the action economy article made it sound like you'll also be able to Ready an Action to be used as a Reaction in response to a trigger you set up, just like in 5e, which I am thrilled about. This is my absolute favorite incarnation of delaying actions I've seen, so it's great to see PF2 adopting it as well.
I'm a little curious how dual-wielding will work. If going sword-and-board gives me the option of attacking one, two, or three times depending on if I raise my shield and/or move, what will the benefit of holding a second weapon instead of a shield be? Even more attacks? That seems like it could lead to lot of attacks per turn if so. It'll be interesting, for sure.