I'd love to have seen Tuvok in red, serving as Janeway's XO (something that would re-establish their friendship) then have him replaced at tactical by a woman (I did think Ayala, but there hasn't been a woman as security chief for far too long--even then she didn't last--so they need one in the role). This role could have gone to Jeri Ryan as Lieutenant Annika Hansen, just lose all the Borg implants and backstory.
Replace Kim with an alien officer (Benzite, Deltan, Napean, etc).
Have a random crewmember decide they don't like the uniform and is willing to take over the galley, then become a minor recurring character (I think Chell would work in nicely here, we just to know someone's cooking, we don't need any stories about them).
Commander Austin Harris, First Officer, Deep Space Nine (by FltCpt. Bossco)
8.01 - Darkest Before Dawn
(Chapter 8 added, 12/09/2015)