Shea and palm have a similar profile in many ways, although shea might well bring something else to the party (some people notice a difference with shea, others don't) but I would not use the shea - as a superfat in HP, yes, but not as a saponified element. For one thing, at around 30% you might start to cut down on the lather, as butters in that sort of range have been known to make lathering harder. Are you averse to lard? ("If loving the lard is wrong, I don't want to be right!")
There is nothing about the lye discount on this - at 5%, I would not like having so much CO in there personally. Have you used a 20% CO soap before?
I wouldn't say it would be terrible as a recipe, but I also do not in any way love it.