Technically there was already a way to overwrite WEBROOT.  You would just define it before including the Composer Autoload file.  In the  bootstrap, it was checking if it was already defined before defining itself.  But I actually like this way better :).  I'll have to do this for the cache path as well.  Because people are wanting to change that as well now (due to every time you update Munee, it wipes out your cached files and they have to all be remade).