HU, I don’t know if what I have to say will help. I discovered that oven makers are making 24” ovens in Stainless Steel. I have ordered two 24” Frigidaire ovens that are nearly the same size as the old Thermador. The appliance dealer’s installer came and said he would figure out how to make a divider, and a mason contractor I had for another job said he could resize the brick wall, but I guess it’s up to the appliance installer to put in the divider board. So check with your appliance dealer to see if his installer can figure out how to support the upper oven.

I have a 36" range top with a Wolf single oven, Advantium 240 above. I use the Advantium for almost everything I bake/roast, except for larger things like turkeys and roasts.

We did option 1 and I don't regret it at all. We have a small countertop microwave that is in a regular upper cabinet with a smaller door - picture below which is much easier than explaining! (Just avert your eyes from any unfinished trim bits you see!) This is the first time I've ever had double ovens and I am still surprised at how often I use them - it's so much easier to plan meals that have two different oven temp needs. It feels positively luxurious to be able to have several different things going in the oven at once! Also--before we renovated, our kitchen had a fancy Kitchenaid combination convection microwave/oven like in your option 4. We had so much trouble out of that thing. The microwave had to be repaired a couple times, and the oven electrics would freak out and stop working every single holiday we hosted! We kept them both limping along, but since they were attached, we would have had to replace both appliances if one of them totally broke.

Is there room to do a microwave drawer in the island or one of the perimeter base cabinets? I wouldn't stack three appliances on top of one another. Whichever one is on top will be tough to reach, and might be a safety issue when trying to pull something hot out of it. I specify microwave drawers a lot. They work great and they're convenient.