If you are constantly removing nails and such from the tires then airless would be the way to go. If it was just the occasional nail something like the bibsteel might work, but sounds like you know the conditions you will be in and what hazards there are. I haven't had to fix many punctures with the bibsteels but that's just on machines running around the farm.
I think Tweel s are around 1k each now, not sure how the price has been lately on them. They are retread able which adds a lot of value. Many solids are not. I notice the mcclarens are pressed on, at least some of them. Probably not an issue for you but in our barns the curbs are the perfect height to knock them off the rim over time. It's happened before with a different set we had, might be a non issue with the mcclarens though.
Tread depth isn't everything, tread compound, curing, and casing performance also plays a role. Radial tires wear 2-4 times longer than bias tires due to the casing more than anything, they generally have similar tread depth. The Tweel still functions like a radial tire and has a pile of steel coil in it. The band you see between the lugs and spokes is full of steel which is what keeps performance similar to a radial and increases the footprint with low ground pressure. An all rubber concept that's Swiss cheesed can flex a lot and create a lot of heat which can lead to quicker wear.