What don't you like about Feser's argument?
By PPC the first cause has to have all perfections, since it is the cause of all things.
You could also check Joshua Rasmussen's work. He has some really good articles on cosmological arguments. And he defends a conclusion quite similar to "pure act" in his arguments for maximal greatness. Check "An Argument for Maximal Greatness" https://www.youtube.com/watch?v=t_trdgsMdyQ (there is a link in the description for his paper). His basic argument is that the foundation of reality (i.e. the prime mover) can have no arbitrary, unexplained limits, so it must be maximally great, maximally powerful, etc. Otherwise there would be no explanation as to why the Foundation would have this specific limit, etc.
(And I think we can put this into act/potency terms, as of course a potency would be like a limit, there would be a question of why and how the prime mover would have unactualized potencies, why they wouldn't be actual, etc).
He's also currently writing a book on God's existence, so you could check it out when it comes out.