Wagtail
Horse servant
I'm going to go against the grain here and say, yes it could work, but not by stabling the horses most of the time. You want a manege to school in, but you have to be prepared either to use it as turnout too, or to build another, separate all weather turnout area. So long as the horses get adequate turnout time, plenty of forage and other exercise such as riding, then with careful management, two horses could be kept on 3/4 acre of land without seriously compromising welfare. No reason at all why they can't enjoy 24/7 turnout in the summer so long as supplementary forage is provided. Much better in my opinion than the thousands of poor horses kept alone because their owners think they don't have enough land for company. It is not an ideal size, obviously, but if you don't stable for long periods (by providing alternative all weather turnout) then I think it could work.