I highly appreciated support from the thinking part of the members of this forum; however the quantity of the people who never used their own brain yet is quite frustrating.
nice way to insult everyone on this forum there vlad.
the first time you posted i was already very annoyed by your multi board spam.
But nevertheless, let me try to, put in simpler terms, what you're trying to say.
Outview
1a) First you're going on about note strengths. Simple.
2a) suddenly this ... computer program comes in like a product placement. I've no idea where this came from.
Inview
1b- something with lots of plusses and minuses. STILL utilising the traditional notation, but after that expanding on it
2b- okay so what this program will do... if you input a recording (live/midi) and then it'll display for you the sheet music, with your note strength notation. Then allow the user to change these, note strengths, timings etc, and then it plays it back to you the way you'd want it to be played. So that way the user can then use this as the basis for his/her performance.
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my views
1c- right. Lets take your fine example of the fur elise
Today my concern is in the very first bars of “For Elise” by Beethoven. Which notes of the melody E-D#-E-D#-E-B-D-C-A C-E-A-B E-G#-B-C should be stressed, played stronger than regular ones (you can mark them with “+” or ”++ “or “+++” depending on Note Strength), which should be softened (mark can be “-“, “- - “ , or “---“) and which notes are just regular (not stressed, not softened – no mark needed or mark “0” can be used).
and xvimbi's fine usage of your notation
overall p (equivelant to 0)
E--
D#-
E0
D#+
E++
B+
D0
C-
A---
(crescendo to the last E, then decrescendo)
so expanding what you're saying is you want us to read
EP-- D#P- EP D#P+ EP++ BP+ DP CP- AP---


?

FURTHER MORE, you don't exactly state WHICH OCTAVE the notes are on?... so now what do we get?
5EP-- 5D#P- 5EP 5D#P+ 5EP++ 5BP+ 5DP 5CP- 5AP---


?

oh wait... you mean with a score? alright then...
here's an original edition of the fur elise. M1

here's vlad's, which i made

here's a more extrapolated copy of the original which i edited

right... TELL ME now... is it easy to understand ALL THREE? in fact... is not the traditional notation there EASIER to read at first glance? even with my extra notation added on, its still easier. of course you'd probably say no. and i don't blame you. You have a cause to champion. But do think of others, who don't have your amazing sight reading abilities.
so you say that this would be a valuable tool to teach beginners? alright lets count the number of Basic symbols a beginner would be required to learn.
Traditional
PP,P,MP,MF,F,FF, Cresc, Dim, Forza. (count 9 symbols)
Vlad's
PP,P,MP,MF,F,FF --,-,+,++ (10 symbols)
oh okay so PP is quite understandable once you've learnt P? like wise with -- and -, > <, etc
so
Trad: p, mp, mf, f, sfz, < ( 5 symbols)
Vlads: p, mp, mf, f, -, + (6 symbols) and not forgetting we don't have a symbol for forz.
SO overall you're asking beginners to learn MORE symbols, and read MORE symbols on the score?
Next.
You say first that the traditional methods of notation are not accurate. Since we have no idea what the composer means by P, by F, or the relation between the two. Right, so let me ask you, what is the relation between P and P-? isit SLIGHTLY softer than P. isit a TINY BIT softer than P.isit just SOFTER than P? or isit VERY MUCH softer than P?
That said, however, i very much doubt your notation has the same application as the traditional notation? Who REALLY cares whether a section starts with P, or P-? there'which brings us to applications of your notation. The notation of musical GUIDELINES (or laws, which i so dislike to use).
- ON A SIDE NOTE-
There is a very misled school of thought that P,F has to mean something A certain VALUE. a VOLUME, a VELOCITY.And they must have a relation. Unfortunately that is wrong. P means Soft. F means Loud. P, Very soft, F, Very loud. That's all there is to it. It is only in the later eras where people decided to add in FFF (of course, due to the increase in dynamic range available on the piano). But its because of that that we're misled to think that FFF is three times more loud then ... loud?
- END -
anyway most teachers already have their own method of notation such things. Mine, for instances, draws a line descending over two notes with a slur (the first note of a slurred pair should fall towards the 2nd). simple to understand, isit not? Two lines, to show the high point of a phrase. even simpler. TWO lines. not 10-15 characters.

Okay so we've ruled out your notation for
beginner's notation.
guildline notation
which leaves us with your FINAL application (i don't remember seeing any other), that is, the Conveying of Music in Plain Text. Particularly useful, say, over a internet chat program or....... come to think of it, that IS the only application i CAN think for it. On paper its already redundant. People can write out a score faster than you can write that out and understand it. Aurally? Jeez, whatever happened to singing? Can you imagine a radio program that goes: FIVE-EE-PEE-Minus-Minus Quaver FIVE EE-FLAT-MINUS-Quaver and so on so forth?
And even then, on the internet, with increasing technology there's video conferances, Voice-over-IP,and look above... i've already shown you how EASY it is to post a picture.
Ah yes i forgot... COMPOSERS!
If composers WANT to use it , that's their choice. Its not the first time composers have used their own unique notation to convey what they mean. But in MANY cases, they wish for it to be STRICTLY adhered to. And they're mostly Avant-garde. There is nearly NOTHING that the traditional notation can't do that yours can.
And computer music has been around for awhile already. the last ligeti etude was meant to be played by a computer. So you're kind of late.
So, ultimately, your notation is REDUNDANT.
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Phew... NEXT
2c- I've already touched on this above... Just WHAT is your relation between P, P+, P++, etc??? Trust me i'm a programmer, and i KNOW you need to set values for those. So, lets see... Assuming we have a scale of ---P, to F+++, that means 12 levels. (lets say P+++ = F---). there're 128 volume levels in midi. that's about 10 volume midi levels.
So what IF ... just what IF... i wanted it to be 5 volume levels in relation to the previous note? Say... i have a SCALE, consisting of 60 notes, and i want a gradual decrescendo... can YOUR notation do that? Now... don't say that that'll NEVER happen. because it COULD, if it you do come up with that program I WILL do it.
AH but then... perhaps you'll say that its up to the student to decipher it.. Then i don't think its ACCURATE anymore. hence... redundant, yet again.
Maybe you say we can have MORe levels... ----!! ++++!! right... which brings us yet again back to our number of symbols per BAR. REDUNDANT.
Bah... i'm spent too much time USING MY BRAIN for this drivel.
Anyway, maybe we can just close this topic up. Come back to us, maybe, when you've found a way to improve it. But as of now, this notation is redundant before it even became useful.
ONE FINAL "LAW" that you might find useful ->
K I S S
KEEP IT SIMPLE! STOOPID! 
-bows-
-exit stage right-