I can confirm that none of the 28 Elmarits work well with the A7s. The Summarits and WATE are fine.
Thanks for all the replies. I went ahead with the 35mm FE. Was toying with the idea of the M-mount lenses since I already have some but a bit hesitant to plonk the money for the Voigtlander adapter. Guess I would wait for the 28mm FE next year!