There are some permutations to this that are probably not worth the effort.

For example, webflyer suggests that you can transfer AA miles through Diner's Club and Hyatt to JAL Mileage Bank with a 25% loss. There are some eligibility thresholds and obviously you'd have have a DC card and be a member of all programs.

JAL is currently offering a reduced mileage upgrade award on full-fare Y and W tickets through March 31 of 30,000 miles, so that would vitiate your transfer loss.

Alternatively I don't think JAL has a co-pay on upgrades so even if you had to transfer 67,000 miles to get 50,000 into JAL your true economic loss is smaller.