You just need a small tractor with a 5' bushhog. My FIL has a small Kubota that I've used the last two weekends to do both horse pastures. One of them is 5 acres and the other is probably two. It's great. It's small enough that I can load it onto the trailer and haul it to where ever I need it, mow and haul it back. It's 4WD too so that helps on hills. He bought it used so it wasn't too terribly expensive.
Oh - I'd love to have that, but that's a few dreams from now!
We had a Kubota with a 5' mower, then as we had 6 horses we found we didnt need it and sold it. I am having to use a john deere 52"? ride on mower and I have been mowing the fields all afternoon, until I couldnt see my hand in front of my face it was so dark. I need more horses or my tractor back!
I like the sound of the 15' wing mower! : )