They haven't said they would be charging for the kit packs yet so I'm waiting for 2nd March. I'd love a building kit of windows and doors for example. If I had to pay for them I could opt out of more clothes for kids & teenagers but opt into a kit of new clothes for adults and elders. Small packs could enable more Simmers to not overload their machines.
It could be a way to keep a small core Maxis staff busy whilst the rest go over to producing a new Iteration and keep Sims 4 alive and not finished with, like Sims 3. The fact that Simmers still want Sims 3 and play it proves that.