Hard coded encoding for all input

I have created the beginnings of a 'cli' and api based on mustache.java
https://github.com/DALDEI/mustache-cli

This is primarily intended to integrate the API portion into xmlsh as an extension module
https://github.com/DALDEI/xmlsh

The first need I have is to use native Jackon Node objects as data, and use mustache template files that produce text serialized JSON.

There are multiple issues I am working through - one I ran into is a hard coded encoding for creating Readers and Writers. The readers use either the system encoding or UTF-8, and I havent found OutputStreamWriters that are not in test code.

To solve the input side I have had to subclass MustacheResolver to override the default encodings.
( xmlsh allows runtime settings for all encodings input and out ).
Do you think it is reasonable to provide for a setter for the encoding used for creating Writers in the core code so one need not subclass just for this ?
I can make a proposal change and submit a pull request.

Start by tracing the core Reader and Writer creation paths and compare them with the MustacheResolver subclass described in the issue; the payload does not name specific files or tests. Confirm where the system encoding or UTF-8 is selected, then define the requested configurable encoding behavior and verify it with the existing test code.