>  How do you feel about pluralism in the other dirs?
> 
>   bin/    => bins/
>   lib/    => libs/
>   doc/    => docs/
>   contrib => contribs/
>  
>  or are these ok without the 's' suffix since they are abbreviations

It's mixing apples and orange; keeping needless brevity while trying to 
maintain some formal grammatical correctness.

binaries
libraries
documents (or documentation)
contributions

James