This sounds a bit obvious, but after years of reading the indoor/outdoor cat debates I finally just started taking my cats outside into the fenced yard for supervised hour long play times each evening. It kind of meant a paradigm shift in thinking about them as cats. If I had a dog I'd have to walk it for an hour a day. I never considered devoting the same amount of time to the cats. Most cats don't enjoy being leashed, and though mine have leashes, it isn't fun for either of us when they are leashed. Turning them loose in the yard unsupervised is a bad idea, for all the obvious reasons. But it struck me that just sitting on the porch and keeping an eye on them while they play is really the perfect answer for these cats. They are middle aged and have always been indoors, but this house has lots of windows and a fenced yard. One of them often cries at the window as though she wants out.
Now that they are out they basically just graze like cows for the full hour *LOL*. They kind of poke around, nibbling, staring, and wandering aimlessly through the grass. They pretend to stalk birds (but never get near enough to do harm). They sniff everything. They seem really blissful. They are also sleeping better and begging for food less.
I do think unsupervised outdoor cats are a nuisance in many ways yet I also think a cat living strictly indoors without ever having time in the sun and grass sounds just as sad as if a dog lived like that. Don't all animals benefit from time outdoors? This really feels like a great solution.