Jens, that's a good start! A few things off the top of my head:

1) Consider the spelling "y" for /j/ instead of /j/. My gut feeling is
that that would be more internationally recognisable. I have no proof
of this.

2) The association particle "da" is a fine idea. Consider also a
modification particle that works the same way, which would help to
distinguish modifiers from nouns, and modifiers from verbs: 'happy
-like- student'. (Ceqli and Mandarin have such a particle, though it's
optional.) Otherwise, since POS is not marked, it becomes hard to tell
when something is a modifier rather than a headword...the result is
"headlinism", in which you have to read or hear something several
times to parse through the possible meanings.

3) What will the compounding mechanism be? Simple juxtaposition?

I'll have another peek at lunchtime.