It only takes a single point mutation to "make a new function" that allows people to resist malaria.
The fact that a new wing would not be immediately useful is an interesting counter-example, but I bet it's self-evident to most readers that using a new wing is going to take neural and other changes due to the complexity of aeronatics, whereas lengthening a body part, or even adding a new limb for ground locomotion, is not nearly so complicated.
First of all you are assuming that it is a mutation. Second, this mutation is absolutely deadly and would destroy any group in which all members had it (because it would kill 25% of the population each generation). This is very destructive and in no way supports evolution. What you need is beneficial mutations and those cannot be found anywhere. There is also not a single example of any organism - virus, bacteria, fruit fly, or whatever, which has ever in the numerous experiments conducted on them been transformed into a more complex creature. Not one.
Is this truly a mutation if the ability already existed?