I could not be happier with Logos in the last couple of years with adding the multitude of Puritan resources. Just too wonderful!
Logos should seriously consider adding Robert P. Martin's "A Guide To The Puritans" as an offering. He indexed an extensive amount of Puritan resources by topic and by scripture reference. I use it a lot (I have a large Puritan library) to find Puritans that speak to the verse or topic at hand.
Mr. Martin's book doesn't index everything though and I have a Google Doc I created that supplements his work. My doc only indexes by scripture verse though.
Still, offering Mr. Martin's book would be a wise direction for Logos so others would find interest in other Puritan resources they may not have.