I don't think introducing an atomweight division would have much, if any, bad effect on the UFC strawweight division. 10 lbs is quite a big difference in bodyweight when talking total bodyweights of only 105/115 lbs. It's a much larger handicap for such a small fighter to fight one division up from ideal, compared to heavier fighters doing so.
Fighters who should ideally be fighting at atomweight will probably not do nearly so well fighting at strawweight. Waterson and Penne were both Invicta FC atomweight champs, but have fallen short as strawweights in the UFC. Recently, Invicta FC atomweight champ Ayaka Hamasaki fought and lost to the Invicta FC strawweight champ, something I suspect Hamasaki only tried because she wanted a way into the UFC and knew she couldn't get there as an atomweight. Seo Hee Ham was badly out-sized in the UFC strawweight division, but is now an exciting atomweight champ outside of the UFC. Fighters who can fight at atomweight probably should fight at atomweight. And there should be a place for the best of these in the UFC.