Core overriding into a module, is it possible?

[daniel]

Hello,
I'd like to change the way netbeans open file to force him download the
file before opening it when the project depends on remote source files.

If I succeed, I'll probably try adding a property for this and submit
it to the core, but to develop it I'd like doing that into a module
instead of into the core.

Is it possible and if so, any one could show me a start point?