I'm going to indulge in a bit of role-play here, hope you don't mind. Now, most of these are Captain Obvious items, so don't shoot the messenger. They may also be in the process of changeover as well, so it may be moot.
Were I the Chief Design Officer, these would be my top five (5) priorities walking in the door -
1) Fix the MacBook Pro butterfly keyboard situation - like it or hate it, believe the hype or not, the situation is still a PR mess that Apple has not handled in a stellar manner. First thing would be to figure out the next evolution of the MacBook Pro and design a chassis that can accommodate a different mechanism.
2) Carry that fix over to the MacBook Air and MacBook lines - cannot have one without the other two.
3) iMac redesign - the current iteration is essentially two revs and 10 years old, it's time. Also, the XDR Display ID would be the logical place to start iterating from for a variety of reason. Love it or hate it, it has its merits.
4.1) Reintroduce a bit more dimension back into iOS and macOS icon, UI and UX design - iOS 7 was harsh and so far opposite that even Apple has pulled back little by little over the years. No, I don't mean go back to Aqua, its day is done, but there needs to be a system-wide rethink of textures, patterns, details and implementation.
4.2) Harmonize the UI styles for Apple's applications to build a better consistency for users to retain and discover the functions inside of applications. Inconsistent toolbar/sidebar icons from app to app reminds me of Windows...among other things that Jony phoned in over the years. He really didn't care once the initial iOS 7 work was done, because he is an Industrial Designer not a software UI/UX guy. Otherwise, we wouldn't have a + button at the bottom of the Reminders app on iPhone, which drove me mad as I tried to discover how to add a Reminder since the bottom make no ****ing sense when its hidden off-****ing-screen!!!
5) iPhone design - the triple camera bump is ugly to say the least, if it comes to reality, the iPhone is slippery as hell compared to the chamfered iPhone 4, 4s, 5, 5s and SE. These are beautiful designs that have stood the test of time and there is gold there to mine for the next iPhone designs, IMHO.
That's it...well, not really, but Jony didn't get to make hardware decisions, I think he did the rough drafts, had others finish it and then he said, build it, and must have had veto power over most, if not all, design changes requested by the Hardware division. Their job was to make it work...that is all. I can tell you, there are some who won't be sorry to see him go, that's for sure.