It is interesting, but I am not convinced it is better yet (still looking for a PF2e game). If I were to go to the effort to bring it to 5e I would make it a 6 action system and include reactions with it. That way you can control counterspell spam, and OAs (similar to how PF2e already does, but it is built into the action economy)I mainly want the three action system. I don't think it's impossible to bring over but it will take a LOT of work. Every spell has to be figured out. Most would just go to two actions but I could see arguments for a few to change number of actions. Movement would need to be reworked. Attacks would need to be reworked. Might be a way to change it to two-actions+movement but that's just as complicated, just removes one of the things you'd need to modify.
With 6 actions you have (off the top of my head):
Move = 1 action = 10 feet
Disengage = 2 actions = 10 feet
Attack = 2 actions (not sure if we should add the penalties from PF2e, maybe when fighters get extra attack you just reduce the penalty, makes them the best fighters)
Cast a spell = variable actions, most cost 4 actions (perhaps 2 actions per spell component or 1 +1 per spell level if you want to nerf casting a bit)
Reaction = 1 or 2 actions
Bonus action = 1 action
EDIT: this lines up nicely with a 6 second round too.