I have been asked recently by several people to lay out an architecture for direct lunar return. This includes what is required (e.g. LOP-G or no LOP-G?), how the pieces fit together and the likely outcome of such a program. I find that almost all of these issues are addressed in a paper that Tony Lavoie and I wrote two years ago:
This 2016 paper (updating an architecture written 6 years ago ) details how to fulfill the 2018 Presidential Directive to return to the Moon. It also addresses how to use the existing SLS and Orion programs to enhance the plan.
As you read it, please note how this paper addresses many questions and talking points being bounced back and forth in the current national debate about the U.S. space program.