Nothing wrong with a 10" wide tire on a stock 5.5 or 6 inch wheel. Sure, it's at the maximum that most people go, and it's well past the "normally recommended" size by most tire manufacturers, but it's been done countless times.
Maybe others here will have done it and run them long enough to let us know if they ran into any real issues while doing so. Maybe odd tire wear, but which Broncos didn't have odd tire wear back in the day? Mine sure did!
Maybe needing to adjust tire pressures to keep them wearing well and feeling good on the street. But that is also something that is standard operating procedure for any non-stock tire-wheel combination.
Good luck.
Nothing wrong with a 9.50. Just feel that if you want a 10.50 then it's worth a try. Just getting one in the diameter you want could be troublesome. After all, you can fit a 33" tall tire with 2.5" of lift. Are your rear fenders uncut still?
Paul