Ranges, and especially wall ovens, nowadays with electronic controls typically have a cooling fan for the control panel that exhausts a larger immediate volume of heat into the room. In any case, all the heat generated inside the oven cavity during cooking must eventually dissipate into the room, short of having a closed-circuit outdoor exhaust integral to the appliance. Gas ovens need a bit more airflow through the appliance for O2 to burn the gas compared to electric ovens.

If you need the functionality of two ovens...whether it's b/c of different temperatures, the volume, or the types of food AND you use your MW for meal prep or cooking, then... Getting a Convection MW in place of a second oven doesn't help...if you need the MW, you don't have a second oven; if you need the second oven, then you don't have a MW Using the second oven as a warming drawer won't help b/c if you're using it as a WD then you don't have a second oven. What it will do, though, is allow you to bake/roast in it and then use it as a WD for the food you just cooked in it while the first oven is still going. We do have a WD + double oven + MW. Yes, both ovens have a "Warm" option and my MW Drawer has a "Keep Warm" option. I use the WD more than an oven as a warmer b/c it's a smaller volume to heat and uses less energy. It also has options for Crisp or Moist. However, if I have an oven already heated b/c I've just used it, I'll turn it on "Warm" and use it as a WD...assuming I don't need that oven for another item. Other than for stews, the MW's "Keep Warm" function doesn't work very well b/c it overcooks the food it's keeping warm. How often do I use them all at once? Several times a week, actually. I have Celiac Disease so I do a lot of baking, etc. and often I'm making something that I can eat similar to what everyone else is eating but I need different oven temps. Meanwhile, I'm cooking veggies in the MW and using the WD to keep the various items I've finished warm. I also do a lot of baking for events (like the 6 batches of brownies + 3 batches of cupcakes Saturday morning for our neighborhood's Block Party that afternoon) and find that having two ovens makes the job go so much faster...it allows more than one of us to be baking at the same time as well as allows us to bake more than one type of item at the same time. So, in the end, it depends on your needs. BTW...I tried a wall oven mounted under the counter prior to purchasing my appliances and found that it was even lower than the oven in a range/stove. So, before you plan for an under counter oven, go somewhere and try it out. OTOH, the top oven of a double oven set is probably too high for most people...unless you put the bottom oven just over the toe kick. I think the ideal setup is two single ovens mounted in raised cabinets...i.e., mounted so that the cabinets are 6" to 12" higher than the standard. Oh, and about the location of your WD...when polled here a couple of years ago, overwhelmingly it was found that if you had your WD near or under your cooktop, it was used. However, if it was mounted far from the cooktop or too low, it was rarely, if ever, used. The latter included WDs mounted under ovens in an oven stack. So my suggestion to you is to not put it in an oven stack; instead, mount it next to or very, very close to your cooktop.

I have a Miele speed oven and I love it. It's our go to oven and we use it every day. But we only have one other oven-in our 36" range. That said I don't think you need a speed oven since you have the two ovens in your range, both of which are convection. I think all you need is a microwave, unless you really feel the need for a third oven. I love that the speed oven heats up very fast and food cooks more quickly in it, but not a lot more quickly imo. And we like having a microwave but didn't want a stand alone microwave since we don't use one very often. So a speed oven was the perfect option for us. If I had a 48" range I doubt I'd feel the need for a speed oven too unless I was a huge baker which I'm not. I think your smaller oven will be perfect for everyday much like a speed oven.

"4 burner ranges don’t actually use the same amount of space - there is dead space in the middle and it seems like more around the sides too. Whereas the 5 burner range uses more of the actual 30”." The 30" width is the constant between the two choices. The "dead space in the middle and more around the sides too" on the 4 burner configuration is exactly my point. That is why there will be room for your 12" pan and your dutch oven at the same time. If you cannot find the Thermador 5-burner range on display, just go to a store that has several other brands' 30" 5-burner ranges on display, like Best Buy or whatever local appliance stores there are. Bring your pans with you. You will still be able to see the difference in layout and how your pans fit on a 5-burner 30" range vs. a 4-burner 30" range. Perhaps you will like the 5-burner setup. I do not because of the reasons I've stated about fitting pans. Also, I have never needed 5 burners at once, even on Thanksgiving. A totally different approach would be to go to a 36" cooktop. You won't have the industrial look your husband likes, but unlike with a rangetop, you can fit an extra drawer under it, and you won't have the issues of fitting pans, and even have some room to set down pans that aren't cooking. I understand you said you cannot fit another 6" of width. Perhaps post your layout on this forum (post separate thread, entitled with something catchy like "Pls help me fit a 36" cooktop in my kitchen!"). You will need to provide measurements. There are some amazing layout gurus who hang out here, like amazing.