I wouldn't, laser sight and call it good.
I have a 23 and had a laser rear sight and liked it a lot but it quit working so I went back to factory. good night sights would be good too but any optic would be just that much more bulk.
only one I would consider is a small red dot.
It definitely would have to be a small optic, there are only a few that would fit.
They come with 4 plates for mounting:
01 for use with Eotech, Doctor, Insight and Meopta;
02 for using Trijicon RMR;
03 for C-More; and
04 on the Leupold Delta Point.
Read more:
http://dailycaller.com/2015/04/08/gear-test-glock-modular-optics-system/#ixzz3mx1sDC6x