Hey there! The idea of subdividing your grazing and moving the horse along is excellent. Whatever you do, try from the outset to avoid having your horse turn the area into a desert. Always rotate before the pasture gets damaged, and if grass growth is insufficient, keep the horse in a yard and hand feed it there, and exercise it by riding etc.
We have sandy soils here and have grown hedges of tagasaste (tree lucerne) around the paddocks. They grow phenomenally and are taller than a person in a year. Fodder trees like that can provide both food and shelter for your horse, and reduce soil erosion, and create spaces for birds and wildlife. You protect them behind hot wire so horses can only trim their extremities. Whatever you clip off when hedging, you feed out. If you don't have sandy soils, other types of fodder trees might suit you.
SueC is time travelling.