How would you improve Man in the High Castle? Like many PKD books it presents a premise which seems, naively, like a veritable paper mill that you could churn out endless books from--and then barely goes anywhere with it. That's part of PKD's style. Yes, the High Castle universe could be made to churn out whole series of formulaic literature, but it would be just that, formulaic. Go write it yourself--you don't need PKD to write it for you, once he's given you the premise.

It's like Kafka said. If you try to make a river too large, it will overflow and you'll end up with mud. There's a certain size at which a river is just right, and any more just detracts from it.