Outlets. I have three outlets in my garage and wish I had double the amount or had changed the locations of a couple of them.
It also might not be a bad idea to take your plan view and lay out your anticipated equipment in the garage (lifts, air, deep freeze, rack storage etc.)
I have a similar sized lawn and a Bad Boy 54" Maverick with the FS730V Kawasaki. Very happy with it. Got a good deal on it from a coworker. Had about 20 hours on it. If the deal had not come up, I was planning on picking up a Wright 48" Stander B.
From my research, the three biggest...
A compromise on underslab insulation that I see on commercial projects is running the insulation 4' wide at the perimeter. If your GC is worried about the insulation breaking you can always lay down 40 psi or 60 psi instead of the typical 25 psi.
I agree with @ConCretin on putting down 15 mil...
Only thing I can add is we built our home in 2019. 1400 sf ranch in Massachusetts. At the time I did not know that the recirculation line was even an option. I regret not putting in a recirculation line every time I use my kitchen sink which is about 30' from the water heater. Takes 2-3...