Nasals (again!) and a stress-question

Sent this a few days ago - but it never arrived, or got lost, unless the
Finnish government
decided that conlangs are dangerous and can be used as encryption, and reads
through every
mail passing my ISP. I'm sure they're just trying to make me paranoid, those
***.

I'd like feedback, opinions, and I'd be happy to hear what a linguist has to
say about these ideas, so here:

I've been toying with the idea of having two nasals, (which I shall
translitterate m and n) in a language (yet nothing strange, huh?).
M is the usual bilabial nasal stop, while n is "a voiced nasal airstream
(mostly) without any oral articulation", or to put it another way -
"a nasal schwa with both syllabic and nonsyllabic allophones".

Does this seem realistic? Any natural languages with these phonemes and
distinctions? Could I split the syllabic and nonsyllabic allophones into
different phonemes althogether?

I think, however, that this phoneme would easily get assimilated by
following/preceeding stops, and either prenasalise or "nasally-releasealise"
depending on position. Also vowels would (probably) be affected. Right?

(Sorry for the compound-word. I am doing these constructions all the time in
Swedish too. I think it's due to my Finnish roots. It's a beautiful word
though, I think "nasally releasealise" beats "cellar door"... :-)

For the same language, I'm thinking of a stress-rule like the following:
(pitch and stress-accent applied to same syllable)

The last closed syllable (of the root) is always stressed. If no closed
syllables exist, the penultimate will be stressed. One-syllable words, are
only stress accented and several aren't stressed at all (pronouns, etc.).

Does this seem like a naturalistic stress-rule? Why or why not?

I'd be grateful for any answers.

 -- Miekko