https://www.bimmerfest.com/forums/sh...d.php?t=802986
Another thread where somebody mentions the max size you can fit without a lift kit. It's almost exactly the diameter of your goal tire: not as wide again In the rear so that's the main question: you said you found somebody that put on the same sizes as you were hoping to use, not sure if that also included the wider rear tire or if it included the wider rim, but there are some useful references of people that have done very similar tires to your goal that you can use to make an informed decision.
From a look standpoint, I don't think a completely filled wheel well is any better a look than a 2" thin sidewall crazy low profile tire on a big rim they basically are both variants of "low rider". The main advantage of higher ratio will be a softer ride which is a reasonable excuse to fill the wheel well, I just don't think it will look better than the more advised options (one step lower profile than you wish to use). That's why I said get tire scale photos and Photoshop them on your car: you may love the look and it's far more important you like It.
I don't think in the real world you will find any significant difference in road feel between 35 and 40 ratio tires and they will both be obviously very low profile on 22s there is no getting around that. So back to Photoshop: which will look nicer: more filled wheel well making the car look dropped, or a thinner sidewall making the car look more like a racer ?
If I had an opportunity to pick up a set of rims in a style I really liked I'd be working to solve the same problem. I would as I mentioned first aim for closer to 1-2% oversized vs 4-5% for numerous reasons but there is support for going up to the size of your target and does not seem unreasonable, other than I did not see much response to the queries of did you have rubbing problems etc; not a lot of follow-up from the guys that did the oversize mods.