It would be helpful to be able to define multiple page format templates for parts (and scores, too, now that I think about it). A good many of my projects have varying format requirements for different parts. I have gotten by using the save/load library feature to handle this, but it sure makes for a clumsy work-flow. One clear example would be an ensemble arrangement where one player, say a violinist or other string player, needs a larger print part to read from. In these cases, I define two separate parts, one normal and one large print. Another would be defining a "part" to be an alternate version of the full score. That "part" would need its own page properties as well. So being able to define multiple format templates be very handy.
If Finale could do this, you might even be able to remove the distinction between a "score" template and a "part" template, just provide a list of defined templates, and be able to specify a "default" template for the score and a "default" template for new parts (to preserve current work-flows). Then each "part" would be able to choose its own template specification (perhaps in the ScoreManager).