postfix should be the default mta in a chroot jail. It satisfies the needs of the vast majority of users - and I think has a cleaner codebase and is easier to config then sendmail.
In the default case, what's to config?
It's only in the non-default case that things get interesting.
A unified configuration utility is only a problem if the choices offer different and conflicting features. Otherwise you just write a common front end and MTA-specific back ends to edit the files. So first come up with a front end design that enumerates all the features you want to control.
