Yowzer bing.. how many questions... I know some of that... being a bit OCD about this car..
Until the parts are listed there's no way of knowing about the indicators retrofit, however I'd say they will because they'd have to change the wing otherwise and that's cost to BMW. I'm not a fan of the interior I think it looks cheap IMHO, and AFAIK its only in those colours. The rear diffuser is unchanged, its a special 3 part one on the 'is' only. 18i/20i/28i (N20) are 4 CYL, 35i/35is are 6cyl (N54). Depreciation will be bad, as it has been for all models so far, but not that much worse than anything else that's 2 seat currently. Usual 60% over 3 years ish.