I wouldn't go with smaller binos. Scanning with a spotter can be tough if you can't dial it down far enough. I use my binos way more than my spotter for everything. BH sheep are no harder to spot than mule deer, for instance, maybe even easier because they have more white on them. Either way, the only hunt I would consider taking smaller binos would be one I didn't take a spotter. For me that would be maybe an archery elk hunt where seeing animals is good enough, and telling approximate size is is good enough, and spotting ranges aren't too far. For a sheep hunt to pick apart the mountain, I'd want the best I can afford. I've never felt burdened by 10x42s on any hunt, including a couple dozen backpack sheep hunts. I've considered going up to 12x or 15, but I would still bring a spotter, so I'd really not gain much.
BTW Dall sheep can be very hard to spot in the rocks, or when bedded, many times all you can see is from their nose up.