it's very doable but consider other options. What about a barn (if you can get pp) rather than stables? you can make a barn into stables (with gates) and then back to a barn. A lot more useful. In winter they are not standing in stables, they are wandering/loafing in a barn. Doors open and they can wander out to a yard/grazing. In summer they sort the problem of flies themselves by wandering back into the shade of the barn.
If you have a house then the area around that is often a waste of space horsewise. Can you make something of that to give the horses more space? For example our house, buildings etc occupy about 1 acre of wasted space. Not any more. The concrete path along the front of the house is part of a hard track, gate opens onto the lawn when we want it mowed, the hard standing vehicle parking is part of their wandering track. All it takes is a bit of electric tape or a couple of rails to fence of the bits you don't want them on.
We are so short of land in this country that if we move away from the idea that horses live in stables and then get turned out into a field, often of restricted square or rectangular size (due to grass restriction) you can make some really interesting areas for them to live in that gets them out of stables and gives them some freedom.
People with horses at home are so lucky in this respect.