Pointed this out on another thread, but I'll mention it here as well.
Gregor talked with Jean-Baptise on Ace vs Hibana/Thermite. Jean-Baptise mentioned the goal for Ace is for him to be used in situations where hard breaching is risky, like on Coastline according to Gregor. Thermite's openings are still the largest, and Hibana is a 3-speed with solid weapons. I personally don't think Ace is going to ultimately replace either of them and may introduce more variety in hard breachers on certain maps.
Again, I would wait until the TTS tomorrow and actually try playing him to get a better understanding.