I keep things interesting by planning little to none and letting things happen organically. If I do plan, I always find a way to screw that up. lol So my sims are at the mercy of my mind's whims... and aliens.
Also, I never personally keep a specific sim. I have many in my library that I have created but seldom, if ever intentionally bring them even into the game.
However, raising your favorite sim from a child might be interesting. It could work quite well and maybe you'll find out things about her that you didn't know from the choices you make with her as she grows... Why stop at child though? Raise her from toddler and see what delightful chaos she gets into...
