> > Mandarin doesn't, but the native Cantonese name does have it

> I know, but my point was that most people in the world would
> have trouble
> learning it.

Yes, but the intention is to preserve the native name as much a
possible. [n] can be an allophone of /N/ for example. Another option
would be to put and optional schwa in front of the word as well.
Possible would then be:

Nomun, nomun, @Nomun

Notice that /N/ is only used like this in proper names. In the general
lexicon, it is only used after a vowel.