The biggest reason you don't see larger induction ranges is that the 30" ones are already at the limit of most American electrical systems as they exist. 40-50 amp circuits are all that exist currently in most homes in a range location and most American homes only have 200 amp services. If a larger range with larger needs for power were introduced, it would for sure require rewiring as a condition of it's use. And in the typical home, 200 amps of service is already pushing the limit on usage with all of the TVs, computers, and other eletronic gadgetry that are in a modern home. (It's the same reason why you seldom see a retrofit for an electric tankless water heater.) Commercial installations that use large induction hobs typically have access to 3 phase power and MUCH larger service runs. You only have to look at the different electrical requirements between a typical 1970 home and a 2010 home to see how many more circuits are now needed. Start adding in a power hungry range that needs a 70 amp circuit, and you start talking a LOT of money to rewire the run from the pole, a new panel, and the new run for the range. It's just not economically feasable for any maker to introduce something like that at this time. Youd need a paradigm shift in new home construction to make it happen. This post was edited by GreenDesigns on Fri, May 24, 13 at 9:49

Five years ago, when I remodeled my kitchen, I invested in a 30-inch DF Wolf range. It more than meets my needs. On the very, very few occasions that warranted it, the range's 4 burners can accommodate all of my largest sauce pans, frying pans, etc. at the same time. The range is very well designed, with lots of space between the 4 burners, and that is why this can be done. The vast majority of the cooking I do (and I do cook a great deal), involves 2 burners operating at a single time, and sometimes a 3rd burner. Plenty of room between the pans when I use this configuration. I wanted the Wolf range and did not want to subtract space from my kitchen counter top/cabinet design (which is on the smaller side) to accommodate a larger range. I've never regretted my decision to go only as large as a 30-inch range. As far as the oven space in a 30-inch range, it more than meets my needs. I use large sheet pans, roasters, etc., with ease and the cavity fits all of my requirements. But....I drive a Subaru, so I'm not into large cars, either! :) Here are a couple of photos of my kitchen so you can see the 30-inch range in a kitchen setting.

I've got a 27" electric oven beneath a 36" gas cooktop. My GC said the oven didn't actually need a cabinet at all, as long as the base it sits on is level and strong. He built a platform base, on which the oven stands. Then he mounted a panel on the front, with a cut-out exactly the size required in the oven installation instructions. This was sprayed to match my cabinets exactly. The oven just slid into the hole. The panel idea should answer both 1) and 2). However, my GC did suggest that if I wanted to make the whole thing look more integrated, he could cover the visible pieces of the panel with stainless steel (my oven is SS). It wasn't the look I wanted, so we didn't do it, but it could look good. 3) you need to check clearance distances carefully for each appliance: we ended up raising the countertop by about a half-inch in order to ensure the correct gap beneath the cooktop. Not an issue for me, but you need to check the clearance requirements, which will be in the installation instructions or the manufacturer's website.

I have a 36" cooktop over a 27" oven. The oven isn't actually in a cabinet proper: it sits on the plywood base built by my GC for all the cabinets, and then he created a face panel, with the appropriate size hole for the oven, and had it sprayed to match my cabinets. There's a fair bit of panel on either side of the oven, but I really don't mind: I didn't want those spice pull-outs, and wondered about making a couple of 3" tray slots, but realised the space needed internally for the hinges would make it pretty awkward to use, and I decided that offsetting the oven and getting 6" for a cabinet would look strange (in MY kitchen - that's a personal thing). So, I'm happy with my panels. I got my tray cabinet in another place in the end. I think you have to decide for yourself whether you want/need symmetry on that wall, or whether you can live without using that space for anything. In my case, it also means any subsequent owner can opt for a larger oven if they want to.