Redmine

I have been tasked to write an Android (and eventually Iphone) app against our Redmine installation. I have already made significant progress, mostly using the to_json aspects of the restful requests structure. I am finding a recurring situation and am looking for design advice.

I am recurringly adjusting the 'respond_to do |format|', 'format.json' methods in the existing controllers, in order to tweek the responses. This will end up significantly branching me from the current redmine release, but in my mind is the most 'RESTful' way of implementing this.

Should I:
a. Continue down the same path and adjust the existing controllers for my app, and branch from the redmine release.
or
b. Create a plugin for the 'mobile methods', and make all my requests against it. This introduces secondary resources for things like news, issues, etc. It is more modular, but less 'RESTful', in my opinion, because now there will be multiple places to retrieve the same resource from the Redmine instance.

What does the community think: 'Logical Separation' or 'Purest Design'