Here's the basics of my idea.

Looking down on the wing in planform.

Imagine an aileron inboard end was cut at an angle of about 30 degrees to
the chord rather than the traditional 90 and the wing box ( or adjacent
flap ) was cut back at an opposite 30 degrees. The view from above would be
of a trailing edge with a 60 degree trianglular 'bite' missing. Now take a
triangular piece of aileron section that fills the 'bite' and at its apex
install a ball joint. Into the rear of the aileron spar mount a ball socket
to match the one on the triangle. Now you have a triangle section filling
the gap and free to rotate long the ships longitudinal axis. ( gee a picture
would work wonders here !)

By installing a mylar seal along the ( almost chordwise ) edges of the
aileron and wing (or adacent flap ) such that a sliding seal is made with
the triangular piece you might get an aileron / flap joint that doesn't kick
off that vortex.

This might be advantageous at the flap root end helping to clean up the flow
at the root training edge.

It all sounds rather complex but perhaps the .01 % difference it might make
would be worth it.

Any thoughts on this?

Ian

PS: There is a variation on the triangular piece that is more elegant but is
almost impossible to visualise without a drawing!