I plan to someday hike the PCT (distant future) and I was recently watching Jesters video "Wizards of the PCT" if you haven't seen it, you need to!
Anyhow, I talked to Jester about using a hammock on the PCT which has always been a concern of mine. He told me one of the guys he hiked with had a hammock and used it almost every night along the trail (you can see it one of the shots - looks like a Hennessy). So I feel encouraged by that. I've started thinking of what I would do in the few situations where a hammock cannot be used.
My tarp can serve as a tarp shelter without the hammock, I can use treking poles and make an A-Frame. I've got a pad I like to use because it is lighter for the warmth than underquilts, so that took care of sleeping on the ground. To cover the ground I took an old tyvek ground cloth and made a hammock cover out of it - so it can be used around the hammock for a little extra warmth when needed, and on the ground under the tarp when the hammock couldn't be used (4.98oz). To increase the chances of using the hammock I also came up with a couple of dynaglide tree strap extenders to allow use on bigger trees or places where I need longer suspension. On top of all that, my hammock is only 7.98oz with all the suspension and extenders, so it is a slightly heavy pillow for sleeping on the ground with when it cannot be used as a hammock.
So most of the gear is figured out. The one thing I didn't have a good solution to replace is a bug shelter. A sock would work while in the hammock, and a head net for walking around in camp. But having an enclosed space is nice, snd in Jester's video, the Skeeters are monster swarms that don't compare to most other places. So I've been thinking on this a while, how to make an enclosed space that would work with a tarp or a hammock equally as well. I decided that it needed to be less than 9 ounces, so that is what I am using as a guideline for the design.
So back to the floor. If I had to go to ground, I already have a tyvek ground cloth in the plan. So the floor of the bug shelter doesn't need to be solid. I like your idea of a mesh, the bug net does serve as a mesh bottom, and I wouldn't be going in with shoes on, I figured the nanoseeum is sort of tough (I've worked with it before) and I could keep it mostly intact over a long hike. I would put the tyvek under the bug net, and I think it would give the tyvek grip. Thru-hiker has a 3D mesh, but I don't know the weight and don't have any experience with the durability, but thinking through the idea you started, it might do the trick.