In the Hello World example (restxq.xqm), would it be possible to split the file in two with half of the requests mappings be in one file in the other half in the other file.
That's absolutely no problem; you may distribute your functions in as many xqm files as you want, as long as they are all in the http root directory (in future, if that's requested often enough, we may also parse sub-directories).
HTTP/1.1 500 Could not initialize class org.basex.http.restxq.RestXqResponse Could not initialize class
I'm not sure how you did this. Could you build an sscce (self-contained example)? Christian