I would not recommend buying a full-fare economy ticket and upgrading with miles. This is a commonly held view, for good reasons. I would use the miles to buy a promo business award outright or a classic award if I had to. The cost of full-fare economy is prohibitive.

Ah!! I see the issue Alan, thanks for spotting it. Sorry Tina. It is a JAL ticket!!! Then I do not know - but it still would be unlikely to be a good idea even if it is possible - again because of full-fare economy cost. Someone else will know this, but I suspect that although you can buy a ticket with miles on JAL, upgrading with miles is probably not possible.