Unifying readers

I'm trying to write a JSON reader based on the new split of packages, but am finding that I'm repeating a lot of the code on the Spark side, so I was wondering whether we can come up with a more generic way to deal with creating readers (fixed vs var len) and bring those methods to the Reader trait. I tried doing something along those lines in https://github.com/tr11/cobrix/tree/unify-readers but I'm not sure if that's the best approach.
Ideally, I was looking for a solution that
- creates an iterator of records that is independent of the type of file we have, so all the methods should be defined in trait vs in specialized Var vs Fixed readers
- push all the logic to the reader package, including parameter processing, etc
Any thoughts on this?