You might also find https://web.archive.org/web/20130512065149/http://www.andong... interesting. The theory is that since you only ever have a space after a comma, you can use it as a dead key, and just have ", " output ", ". That then frees all the other letter combos to be whatever key you want.

There are other keyboard layouts out there with the same concept too: https://github.com/workman-layout/Workman/tree/master/mac#wo...