To understand domestic healthy stallion management possibilities better, we should review what happens in nature. There are 3 different ways in which an entire male horse is "managed".
The Harem stallion is one which has a group of mares. In time, those mares will produce colts, & those colts will reach sexual maturity. There may be a few who stay within the harem herd, even assisting the dominant stallion with managing the herd (but not breeding mares), but most will leave & seek a situation in the second "management" arrangement.
What is rarely seen in the wild is the lone stallion. He is usually the old horse which has been driven off from his harem herd by a younger interloper stallion, & is waiting for the passing pride of lions to jump on him & eat him for breakfast. Understandably, this is not a happy situation for a stallion, & therefore should not be replicated in a domestic setting!
The ultimate "harem stallion" domestically is of course the stallion which runs with mares. We do not really recommend that, as there are obvious inherent risks to both stallion & mares. When lecturing, I invariably encounter someone who says "well, our stallion's never had a problem...", but the fact remains that he only needs a single problem if it's bad enough, & it's all over. What one can do however is have the stallion in a separate pen or stall adjacent to & in the sight of mares. These mares will then become "his" herd.