Neal, I've just had another read through 5.1.
here are some questions:
1/ Are the character/leader names all necessary given the list is now based on 10,000 years since the HH? I would imagine a lot of attrition has happened and even if it hasn't, many of the preceptors would now be higher ranked - if the rank system is still used anyway. I've been finding the changes in the cult lists to character types (moving away from the standard BL standardised naming) slightly confusing. It makes me constantly wonder what that character does in game and I have to ask each time? The World Eaters list suffers from this unfortunately too. I understand the propensity to want a change - heck even the Space Wolves characters are renamed. The thing with them however is they sort of still reflect standard Codex types in their names.
2/Is the preceptor necessary, apart from fluff? Seems like the Adeptus Lord and Preceptor could make a merge. Or is it just a cheaper version to add to Neophytes?
3/Do the Terminators have to be called "Rubric Terminators" as opposed to "Thousand Sons Terminators?" The standard power-armoured marines are just "Thousand Sons Marines" and have the rubric rule also. EDIT - After reading the Battle of the Fang novel I see they should all just be called Rubricae Terminators or Marines.
4/I still think the Defiler in the list could make way for the Deceiver alone. All it needs is to merge the weaponry options into the Deceiver i.e Both share the heavy flamer and claws option and the Tzeentch cannon is the same stats as a battle cannon on the Defiler. Just add the ether cannon and warp flame in place of the reaper cannon and you're done

6/What is the Thousand Sons Adeptus' weapon? It's not listed.
Just some thoughts anyway.