... the only major weakness...
Except that part where your key has to be as long as your message...
is it possible the pear-shape is actually caused by the acceleration?
is it possible the paper's authors haven't already thought of that?
How would you change if you were twice as smart as you are now. How about ten times as smart? (Don't answer, truth is, you're not smart enough to know).
And yet, the author is smart enough to know that aliens wouldn't be interested in humans/ interstellar travel. Good job.
The only perfect science is hind-sight.