First of all, I agree that you shouldn’t use a leaf blower in the aisle when the horses are in the stalls. Absolutely. I also agree with holding the blower low to the ground and using the available breeze or a fan to help things along.
In a smaller barn; it’s easier to work around a horse being up in a stall - put that horse in an end stall, sweep that section, blow the rest of the aisle in the direction away from the stalled horse.
I was so concerned about a dusty environment that twice a year I stripped stalls and power washed the entire barn interior, getting all the cobwebs and accumulated debris off of the stall grates and walls.
A barn that routinely blows the aisle with horses up would concern me, and I’d want to know why. Is there not enough turnout so there’s always something in stalls? Are the aisles so long that sweeping takes a crazy long time? Has the BO/BM had so much trouble hiring and keeping staff that they’ve given up on someone sweeping the aisle correctly?
However, I think the larger point here is that larger barns have a one size fits all approach that makes it less likely special requests can be accommodated. The OP is much more likely to find a barn that agrees with her view or will accommodate her if it’s a small barn and handful of boarders or a small staff.