Well.. i once made a script that goes from ssa/ass to hundreds of layers (and solids :P), but i didn't know how to get the xy-position of a syllable so i needed to that by hand. But basically it's the same as you want to do. And I have to say I didn't really like making hundreds of layers.. it was all in precomps and whatever.. but when i didn't like the font i had to through all precomps to change it >_< (blame adobe for not making font properties expressable).
And for effects (like particular)... you can just save a template of that effect (ffx) and use the applyTemplate function to apply it to a layer in a script.. that may come in handy
