Emily could also send you a letter the morning after the proposal letting you know what things are needed to make a wedding dress and/or tux using the sewing machine. I think they are both clothing items you can already create using the sewing machine. If I remember there is also a veil you can tailor (I would check the wiki to be sure and say which items are used but it is currently down).
Also, I don't know if the existing dress is dyeable or not but that should be an easy fix that would allow non-traditional dress options. Not as special as Emily creating special clothing but maybe something that is easier to add to the game since it would be using previously established game mechanics.