In over 100 international upgrade requests as an EXP, I've been in coach only once, so I'm very confident your upgrade will clear. As you know, you have to buy N or higher to have any chance, but given the tremendous slowdown in paid premium international travel over the past year, your chances are very good.
Check the number of I and D seats available (with something like
www.expertflyer.com ). The more D and I available, the better your odds.
There's no way around the fare class issue, but like I said, you'll likely be in biz class, so spend the extra $150.