I think we can fairly assume that 100 octane was used by at least a couple of squadrons in BoB in sufficient numbers to justify the addition of a 100 octane spit as an additional plane.

So that's for the wishes.

What I understand though is that the devs clearly said there won't be new planes for Cliffs of Dover so I have doubts that we will see it. As implementing an additional 100 octane Spit is the same work as modifying the existing one it won't matter imho.