Adapting legacy lenses is fun and I have done that for many years. Especially like C/Y Zeiss Contax, Olympus and some of the Takumar lenses.
However, while certainly charming, none of these reach the image quality of modern designs. You lose sharpness (especially the corners), you lose AF and you lose EXIF data (which is important for IBIS to work, although you can manually dial it in somewhere in the camera menu of the A7ii etc) and also for automatic lens correction.
Eventually you will end up with native glass.
Why not take a short-cut and start with the FE55/1.8 ?!