My advice is plan ahead. Where do you see yourself with the hobby a few years down the road. Don't spend a ton of money on a fancy 10 gal kettle if you think you may want to brew 10 gal batches at some point. Even high ABV 5 gal batches could be tough in a 10 gal kettle.
I used a 9 gallon kettle to BIAB 5 gallon batches for a year or so. It was tight and had to be watched closely when coming to a boil but it worked.
Later, I built a brew cart around my process using 2 16 gal bayou classic kettles (bayou classic 1064 which now appears to have a thermometer. Mine do not.). They came bored out for and included a bulkhead and ball valves. They're not fancy, some will say they're too thin, etc, etc, but they've met my needs very well and produced a few hundred gallons of good beer with ZERO scorching...
Short answer...YES to the ball valve.