What 4 admin buttons do plan to have top-center?
I assume the two buttons above the P1/P2 player buttons are for coin and start.
I planned on four, but can only think of two I know I need. Esc & Shift. Thoughts?
For the row of four the main ones that I'd recommend are Esc and Pause.
The only reason to have a shift button is to avoid having dedicated admin buttons. (See
here in the wiki and numerous threads on shifted functions vs. dedicated admin buttons.)
One button to almost always avoid putting on the CP of a dedicated cab is the Tab (menu) button.
+10,000 if you have kids or any friends/family members that are not-so-tech-savvy -- after you spend months getting everything just right, they can make a mess in 5 minutes that takes you longer to clean up than the original setup, assuming you find all the changes.

If you haven't done so yet, get your software -- FE and emulators -- installed and configured
before you drill holes in your CP.
That will tell you what buttons you need to make your cab work the way
you want it to work.
Check out the suggested design process
here in the FAQ.
Scott