At this point I only have a concept for it. This version of Primus will definitely be more powerful than the 1e version. I don't believe it has received stats in any other version. I have him tentatively place at CR 40, but that may change. I plan for Primus to posses one of the Elder Spells which makes it one of the 8 most powerful entities in existence.Do you possibly have a rough draft for Primus? I may need him in my campaign.
That being said, I can add him to my to do list:
1) Finish Demon Lords and Princes - by the end of the year
2) Finish Iggwilv - by the end of the year
3) Finish Bahamut - 1st of next yeaer