@Heather Spencer I'm not a pro but I dove into the ventilation question a bunch when I was looking at what to do in my own kitchen. There are a ton of posts on it here, too. ventilation is pretty location dependent as far as what you can get away with, but what you should do is use a hood that's sufficient for the range you buy, and provide the makeup air system that's required for it. If you are anywhere that has cold seasons, or if you live in a tight house, you need to have makeup air. Passive systems work in temperate climates, but not so great in cold climates. The makeup air system is designed to prevent a backdraft situation with combustible appliances. In a cold climate with good insulation, houses don't leak, which means your hood vent will suck more air from your house than can be replaced by leaky doors and windows, causing a dangerous situation. The higher the CFM, the harder it is to replace the air without a system in place (gas dryers, gas water heaters, gas fireplaces, and even bath fans contribute to this calc). For a 48" range you need a serious range hood (Wolf recommends 1100 CFM for their 48" range if I remember correctly). Anything over 400 CFM typically requires makeup air. I ran through the calculations in the code in my state when I was trying to decide on a range and found out that it didn't take much to throw me into full makeup air system, so I decided to go with induction. If you choose a 48" range and pick a lower CFM range hood, you'll end up with smells and smoke, unless you just have the range because it's pretty and don't do more than boil water or make grilled cheese on it. So, in order to do it properly, it costs money. More in cold climates, where makeup air needs to be heated. Less in temperate climates. My builder estimated about $5-6k for the makeup air system (not including hood). I priced out what I would need from fantech, and it got me close to that number. So it is true that the ventilation + hood can be as much if not more than the range itself. ETA: this isn't specific to 48" ranges - Wolf recommends 500 CFM hoods for their 30" dual fuel range, so it's more about the power of your range than it is about the size of it. But generally the bigger your range, the more power it has.

From what I have been reading in this forum, the dealer network for Ilve is mostly going away in the US (if it hasn't already). It's now been rebranded as Hallman and sold through a different channel; you can often find it in big discount chains. Customer service for both brands sounded somewhat unreliable. On the other hand, LaCanche stands out for their amazing customer service. Both the US and the Canadian representatives regularly pop up in this forum and give excellent help. If looks and features are important to you, and your budget is open to it then I would definitely consider that brand. It might take a little bit to receive the order though. My brother just bought a stove and had it delivered to Germany. That took almost 3 months, and he is still waiting for the matching range hood as that was delivered incorrectly. I can only imagine that shipping from France to the US is going to take longer.

I had a 60” Viking dual fuel range in my last house that I really liked (even though almost everyone on this site hates Viking) but I’m really only commenting because I was also concerned about grime collecting under the range because it was up on legs too, and it turned out to not be a problem at all! It was quite easy to clean under it as needed, mostly I swept under it on a regular basis, but the mop was easy to get under it as well. Every so often I actually got on my belly and got under there, but not on a regular basis and it was never disgusting under there. Hope that helps! We had it for about 3-4 years before we recently sold our house to move cross country.

Take a look at the GE Twin Flex oven. You could get that and a 36 inch cooktop and have plenty of cooking flexibility/capacity for less than the cost of a 48 inch range. Won't eat into your cabinet space either. I've had a Twin Flex for two years now and am surprised by how useful and versatile it is. I've yet to run into capacity issues, though I often cook for 10 to 12 people. I'm especially pleased with the Air Fry feature. It works really well for fish or pork tenderloin -- the exterior gets nicely browned but the interior remains tender and juicy. I know you didn't want a GE, but this is a nice oven. (I had space for a built-in microwave above mine, though just opted for a cubby to put in a plug-in countertop mw. Glad to get my counter space back.) https://www.homedepot.com/p/GE-Profile-Profile-30-in-Smart-Double-Electric-Wall-Oven-with-Convection-Self-Cleaning-in-Stainless-Steel-PTS9200SNSS/315999217