Well... FINALLY we have an expansion pack that complements and enhances this challenge perfectly!
When the expansion came out 4 months ago, I had thought of checking back into The Sims 4, but was busy, and it fell through. Now that I have time, I finally got it, and it percolated all these ideas on how to fit the expansion to the challenge's narrative.
Been testing the expansion out for two weeks, and I finally have an idea on the gameplay rules for the expansion. You can see the ruleset at the right navigation bar, or on this link: https://sims4timelordchallenge.blogspot.com/p/life-death-expansion-pack-gameplay.html
Anyway, this expansion really has revitalized (or regenerated) my love for the game. Previously, I've been forcing myself to play it, but nothing really "clicked" with me. I do love Time Lords and Time Travel, and "roleplaying" as one through The Sims is what I had enjoyed when I created this challenge.