Currently Finale has some powerful MIDI options that make VST playback in a DAW possible, but there are some serious limitations that create massive headaches.

1: No CC1 + Velocity options with Human Playback. Some VSTs use CC1 for dynamics with velocity for attack.

2: No ability to use multiple VSTs on the same staff. This can kind of be solved by using a second MIDI channel for layer 2, but expressions, program changes and the like only apply to layer 1 and thus require some serious noodling to get layer 2 to behave. Not to mention that it's really annoying to write Flute 1 and 2 in separate layers. Finale already has the ability to split stacked notes into separate parts, it would be amazing to expand that functionality to route playback of stacked parts to different playback channels. Dorico does this, so I know it's possible. 

3: Programmable techniques in Human Playback. When a technique is officially supported it works almost flawlessly. However, if there is something that you want (Portato, or a2 patches for example.) the only way to implement them is to use a custom text command.  Those technically work, but I haven't been able to make them work in conjunction with Human Playbacks built in options. It's either A or B. (So far.)

4: The ability to view, change, and assign playback functionality to different techniques and symbols. I know that this is already possible to some degree, but it is unintuitive, and seems to be designed to work behind the scenes where users can't view how or why something triggers an action and something else does not. For example, How does Human Playback interpret and execute commands like "pizz" or "section passage"? It would be wonderful if we had a dialog where we could view all executable commands in a list view with the option to add, remove, or change functionality. 

5: CC and Tempo editors. Dorico has a playback editor that essentially functions like a mini DAW. The way you are able to edit MIDI and tempo data, including CC and velocity data, for playback is incredibly valuable. I know Finale has a MIDI editor, but it is extremely clunky, dated, and barely functional. Adding some updated MIDI and tempo editing features that give you complete control over HP's Playback would be an absolute game changer.

Those 5 things would solidify Finale as the best notation product out there. The engraving side of things is already the best in my opinion (having used all 3 big names).  It offers the greatest control and flexibility out of the there, albeit with some clunky draw backs here and there, but it's playback and MIDI control are among the weakest of the 3. I love Finale, and would love to stay with Finale, but I'm growing increasingly dissatisfied with how playback is handled, and am constantly being pushed closer and closer to jumping ship for a competitor that has the functionality that I need for my workflow.

As a Finale power user for the last 17 years, I would love to see it grow and evolve in the playback space to keep those of us who really want to stick with Finale happy.