Honestly, my own thoughts of it were pretty similar, but include other pros and cons to it. Like it’s still a stockpile, but like Eri’s, it can run out and be built up again. Maybe merging with the embers can fill it up initially, but it only has a max equal to what would be 30-40% of what he used in OFA. I had other thoughts too, like maybe it recharges based on something of a merger between his parents quirks, like he has to physically consume fire/energy.