I don’ think that a cdf will take 40mm tyres. Or if it does it won’t have alot of room left over for mud. 45mm with mud guards just no way. I think the bikes that get near are the specialized AWOL, Specialized Seqouia and Kona Sutra LTD. The AWOL might work for you It looks like its 1×11 and hydro. I wanted a road bike that could go off road, not a rigid off road bike. I think the AWOL would work well as an offroad bike
But 35mm and 38mm seem fine to me, round here, for my uses. Your mileage may vary
I do have a photo of the chain stay to tyre gap on a CDF with 35mm tyres if you are intrested
OP either you don’t own a car and therefore the emissions from making you a bike would still keep you quite low in foot print in world terms
Or you do own a car. In which case the emissions of making a bike that you say keep for 10 years are back ground noise