Thanks for answering. Then again, what is your understanding of "modern" : clean and high contrast, I guess ?
The thing that puts me off with the 35/1.4G is LoCA wide open. The Sigma is much better, but its bokeh is problematic (double edges). I end up in using the Zeiss 35/2 much more : lesser aperture, lesser resolution, no AF, and huge vignetting, but its IQ (esp. micro-contrast) and flare resistance are very endearing, not to mention the smaller size (and the small price : 2nd hand, mint condition, 450€).
In the "Art" series, I prefer the 24/1.4, which maybe is less perfect, but has a much nicer bokeh.
The Tamron 45/1.8 would be perfect for my pipe organ shootings : close-up capability and stabilizer... and, being mainly used on my Df, the (theoretically) lesser resolution compared to, say, the Sigma 50/1.4 A would not play a role. What it your opinion about its flare resistance when shooting against bright backgrounds, if you had a chance to test it?