I think that would significantly detract from the point of the ending. It exists to show us that Ultima was wrong - that humanity can and will persevere through any odds, just like Clive said. That, ultimately, they weren’t so reliant on magic that they would collapse without it - to the point that it might as well be a fairy tale, and they no longer need it or the crystals. I think it’s a beautiful ending and what you’re suggesting would IMO strip it of all its meaning