I'm pretty sure my MT is a 10-gallon Rubbermaid/Gott cooler (the big yellow cylinder) so 8 gallons of water in there plus 10-(ish) pounds of grain? I'm thinking that's either going to be very close or it's not enough room. I'm also pretty sure that I'm not totally following the "no-sparge", "BIAB", etc. These terms are causing some cloudiness in my head. If I put 8 gallons of water and 10 lbs of grain in my MT, mashed it, recirced it and drained it, would that be "no-sparge"? And there is NO drawback to having all of the water in there with the grains aside from possibly losing efficiency? Strange. I actually can't believe that at one time I did two sparges. But I was just following orders.
I use a 70 quart cooler for 5 gallon batches but there's plenty of room. 8 gallons plus 10 pounds of grain would most likely fit in your 10 gallon cooler. Down side is possible loss efficiency. Upside is your pH doesn't change when sparging.