Sometimes the most obvious answer is the best…
I'd suggest giving Hail Caesar a serious look.
It ticks virtually every box on your list:
No casualty removal. Units fight at full effectiveness until they accumulate enough stamina markers to become shaken or break.
It was written with large 28mm collections in mind, so your existing armies would fit in perfectly.
Republican Romans, Carthaginians, Macedonians and Successors are exactly the sort of armies the rules were designed for.
It shines with big battles rather than skirmishes.
Most importantly, the command system is one of its strongest features. You issue orders through commanders, but there's no guarantee they'll be carried out exactly as planned. Sometimes a brigade surges forward, sometimes it hesitates, sometimes it just refuses to cooperate. That friction creates interesting decisions without becoming overly complicated.
It's also an excellent solo game because that uncertainty means you can't simply optimise both sides. The command rolls constantly produce unexpected situations, making each battle develop differently.
Is it perfect? No. Some people dislike the abstraction, and if you enjoy counting every individual casualty you'll probably miss that level of detail. But if your aim is to recreate the feel of commanding an ancient army rather than captaining individual units, it does a remarkably good job.
After many years of playing other systems, I found Hail Caesar simply works. It gets a lot of troops onto the table, produces believable battles, and lets me spend my time making decisions instead of puzzling out rule mechanisms.
