I came across a question, well there is more than one question hidden in there. Firstly the obvious one, difference between DI and Separated Interfaces. There's also a package management question in there, as to where to put the interfaces and why.
These are both good questions but should we be answering multiple questions in a single post because like the comment says, it's a little lengthy. How should we deal with it if not?
I'm tempted to continue this onto "Is there functionality to split a question in two? if not, should there be?" but that would be ironically asking two questions in one post