88 degrees Fahrenheit? That sounds great. It will be rarely under 98 degrees in my garage for the next couple of months. The worst is when a drop of sweat falls from the nose, onto the SawStop table saw. I have to be very careful of that lest I risk tripping the brake. I'm using this time to get as many interior jobs done as possible. I sympathize on the heat issue!
Inlaying metal into plywood will be challenging since you have very little latitude when it comes to leveling the surface....meaning, you can't really sand much on plywood because you burn through the veneers immediately. I'm sure it's been done successfully by someone somewhere, but it's not a task I would care to take on.
Otherwise the design is fine structurally, except you'll need to figure out a way to keep those legs from racking.
My thoughts on these guys are well known. Just a guy. A guy with a fantastic talent for making beautiful furniture. A talent that took years to hone. I used to say that most people in this forum could eventually make something that nice, but I'd say that it's likely in the 95th percentile.
I'd love to apprentice at his shop. I'd likely be sweeping the floor and sharpening blades... But, it would be fun.
To answer a hinted question. Guys and gals that use logs start with much bigger samples. Even if you slab that chunk, you lose length as drying checks the ends. If you have ever been in log structures, you see massive cracks that don't affect the structure much. A massive crack in that little piece might leave it in two pieces. Places that make timber structures are often pulling logs from mill ponds after 80 years of sitting on the bottom. They are grabbing barn beams from barns built 150 years ago. Then they cut massive amounts of wood away to get to portions that are least affected. Your chunk might be useful, but the smaller you cut it before it dries, the smaller the useful end product you usually harvest.
I don't want to be overly negative though. Having played a bit with wet logs, I will suggest waiting a year. Seal the end grain with a log sealer, not a finish. Finishes will shed from wet wood. Most cracks will develop in the first year. It may be that a saw cut down the pith will leave you with a block you can glue back together. Just know that most of us would not get our hopes up.
Can't you just make a panel large enough for the top by gluing up less-wide boards? I suppose you could try routing a groove in the plywood and then cleaning it up with a chisel. I'd be worried about tearout, though.