I make, well, my mother still makes, quite a decent chicken soup.
It's ...decent, but I'd like some tips to make it really great.

Here's what she does:
Boil a chicken the afternoon before, let cool and set in the fridge to
congeal the fat.
Early next afternoon, remove the fat and debone the bird, and add
carrots, corn, potatoes, onions, a can of rotel tomatoes and enuf water
to cover. Simmer several hours, and serve at supper. (no salt added,
some of the family is salt sensitive, but its still tasty.)

How can I punch this up to be even better?
What herbs/spices would go well here?
Are there some techniques that would liven it up? Would roasting the
chicken instead of boiling add anything? How bout roasting some of the
vegetables first?

Help me make this a dish well worth inheriting.