I like difficulty in my game.
And I like crawling, plus hate the movement skill 3+, I believe it is. It looks wrong to me and bothered me a lot. When I played Sims 4, I would cheat that skill back down. (The mod to cap skills wasn't available to toddlers.) Movement level 1 was super cute!
I really don't like the idea that toddlers have to be/get fast, but other than that, I think filling in the gap in the baby stage could work well, but I'd still prefer to have toddlers start out crawling.
Another thing I did like was when a toddler woke up first in the morning and went right off clumsily toddling, like here comes trouble! But much moreso if they were twins, that was a hoot for me. Still that later run was a huge no-no, and my frequency of cheating it got tiresome. At least that was my only large complaint with S4 toddlers.