Pglogical is open source and hackable to meet your needs. We're also happy to accept patches with appropriate design discussion and code review to make sure they will aid or not hinder other users and won't add undue maintenance burden.
Rather than repeat the same work, maybe it's worth picking it up as a starting point. It's the extension-based progenitor of the in-core logical rep code, but portable from 9.4 to 9.6 (and soon 10) with a bunch of features that didn't make it into Pg's version yet.
I have no reason to object to your doing it yourself, and you're welcome to use pglogical as a reference for how to do things (see the license). It just seems like a waste.