Would you accept half the battery life/range if it means you can recharge in 5 minutes instead of an hour? In phones, probably not. In cars and trucks, maybe, depending on the specific application. In stationary storage? Quite possibly!
This kind of hybrid may be impractical because it still requires cooling equipment (and its added weight) for the Li-ion, I'm just spitballing here.
1) Lifetime - Historically aluminum ion batteries struggle with cycle life. The aluminum ions are bigger than lithium ions so the batteries endure more strain during charge/discharge cycles. For grid-scale storage, you need to be able to last >10,000 cycles so they need to address this.
2) Scaling up the size of the batteries. Eventually they will need to move on from coin cells and start making larger battery cells. Many technologies struggle to keep their fast charge/discharge characteristics when they scale up in size. We'll see how they do with this.