First time that i have heard of someone using all 3 derate options, seems extremely cumbersome!
Remember that the 25% reduction restriction on assumed temperature applies to the rating in use and not the installed engine. This way you can select 22k and then reduce this by another 25%, this will give you approx a 40% thrust reduction. There is a big question about the financial savings associated with deep derates, how much do you actually save by having the 3rd derate option, when you compare the savings between 30-40%, is this worth increasing the crew workload and the margin of error?
One of the benefits of using the derated engine is the lower VMCG, on contaminated runways this might actually increase your takeoff weight. However this only works for a very narrow band of runway lengths where the aircraft is VMCG limited. Therefore the advantages of using the 3rd derate are extremely limited.
Personally i would recommend getting rid of the 22k derate.
Mutt.