"I'll make a stew of the lot of you"

Question

I'll speak of my letters; though you might be confused:
So many to choose from; so many are used.

I sometimes have two, often three, at times four.
Dot if it helps you; for me it's a bore.

I'm known for my seven, my eight, different ways.
I can see that your eyes have developed a glaze!

I could speak of my children, let their letters be thine:
They have twelve, five and six; one has eight, one has nine.

Of the child with nine letters, to some it is known,
It sneakily has 'nother four of its own.

I've known some great heroes, with their fighting and fun.
Let me know when you've got it. I'm awake when you're done.

Hints:

Although I'm a noun, a person I'm not,
Nor am I a thing. What else have you got?

Another Hint: (for lover of rhyme @Brent Hackers)

When I get a visitor, and when he has been pluck'd
from a burg full of country mice, he'll surely be in trouble.

Another Hint:

A lady of mettle welcomes all to my scene
She's tall and she's French and she's def'nitely green.

Answer 1

Are you

New York City

I'll speak of my letters; though you might be confused: So many to choose from; so many are used.

New York is a city of many different ethnicities and languages.

I sometimes have two, often three, at times four.

NY is two letters and NYC is three.
'Times four' might be a sneaky reference to Times Square, or perhaps NY,NY or CoNY (City of New York).

Dot if it helps you; for me it's a bore.

These can also be written as N.Y. or N.Y.C. but are generally not.

I'm known for my seven, my eight, different ways.

"New York" has seven letters. "Big apple" has eight.

I can see that your eyes have developed a glaze!

"You've got New York eyes/ And it won't take much to fall in love with you"

I could speak of my children, let their letters be thine:
They have twelve, five and six; one has eight, one has nine.

New York has five boroughs. They are in order Staten Island (12), Bronx (5), Queens (6), Brooklyn (8), Manhattan (9)

Of the child with nine letters, to some it is known, It sneakily has 'nother four of its own.

Manhattan is home to "Alphabet City", avenues A, B, C and D (thanks to Chowzen)

I've known some great heroes, with their fighting and fun.

Lots of Marvel/DC comic book heroes originate from New York. Also, Gotham and Metropolis are synonymous with New York so include Batman and Superman. Many war heroes originate from New York as do the brave firefighters and other heroes of the 9/11 attacks.

Let me know when you've got it. I'm awake when you're done.

The city that never sleeps.

Hint 1

It's a place

Hint 2

I think there is a version of the Country mouse/Town mouse tale which puts Town Mouse in New York

Hint 3

Statue of Liberty

"I'll make a stew of the lot of you"

New York City is often referred to as "The Melting Pot"

Answer 2

Some of the connections are weak, but could it be

Punctuation?

Reasoning:

I'll speak of my letters; though you might be confused: So many to choose from; so many are used.

There are many punctuation symbols used, like .,-;:"'?!

I sometimes have two, often three, at times four.

Depending on the context, you may string multiple symbols together. (For instance, quotes and parentheses come in pairs.) Emoticons can use three :-) An ellipsis which ends a sentence of a quote is four periods, or I suppose very surprising statements could get four marks at the end (or more?!?!).

Dot if it helps you; for me it's a bore.

Periods (and spaces, for that matter) are not used in some (often old) writing systems, but they're very helpful for visually breaking up sentences or words. The period symbol is used to make an ellipsis... which sounds like a sentence trailing off...

I'm known for my seven, my eight, different ways. I can see that your eyes have developed a glaze!

Not sure. Maybe seven/eight marks? For instance, .,:;'"!? is eight different characters. You could consider '/" to be basically the same thing, or maybe semi-colon/colon. This explanation ignores parentheses, hyphens, and spaces, though.

I could speak of my children, let their letters be thine: They have twelve, five and six; one has eight, one has nine.

Lengths of names of marks? For instance:
5: space, comma, colon, quote
6: period, hyphen
8: ellipsis
9: semicolon
12: double quote
But this doesn't seem to fit exactly, because "question" is 8, "apostrophe" 10, "exclamation" 11..

Of the child with nine letters, to some it is known, It sneakily has 'nother four of its own.

"Semicolon" is less frequently used (and frequently used incorrectly); its name is just "colon" with four letters added.

I've known some great heroes, with their fighting and fun. Let me know when you've got it. I'm awake when you're done.

Lots of punctuation in stories, especially with action and dialogue.

Answer 3

This is mostly a stab in the dark, I'll probably flesh it more over the course of a few days, but here's my two cents:

Academic Degree.

Why?

Note, I am getting most of my official ideas from this wikipedia article and subsequent pages

I'll speak of my letters; though you might be confused: So many to choose from; so many are used.

Straight from the dictionary. "Letters: the initials of a degree or other qualification." There are tonnes of 'degrees', including diplomas, bachelor degrees, doctorates, and so forth. Each of these then has its own letters, which once again sometimes are slightly different depending on the institution.

I sometimes have two, often three, at times four. Dot if it helps you; for me it's a bore.

Consider Bachelor of Arts = BA (two),
Doctor of Philosophy = PhD (three),
Honours = Hons (four).
PhD and other letters can be punctuated different ways, such as PhD = Ph.D., B.Sc. (Of course this is quite redundant)

I'm known for my seven, my eight, different ways. I can see that your eyes have developed a glaze!

Possibly the different tiers/levels of academic degrees?

I could speak of my children, let their letters be thine: They have twelve, five and six; one has eight, one has nine.

Not entirely sure yet, getting too mixed up with the numbers I already have.

Of the child with nine letters, to some it is known, It sneakily has 'nother four of its own.

See above

I've known some great heroes, with their fighting and fun. Let me know when you've got it. I'm awake when you're done.

There are clearly dozens of heroic scholars.