This is very true, as seen again tonight.
In defence Hayne could just play on the wing, we know he can handle it there - that's where his entire rep career has been played. Burt can defend at fullback, as he knows positional play and does a decent job without as many f**k-ups as Hayne.
After Hayne makes the occasional kick return from the wing (which he's doing as fullback now anyway) he can then just have his current roving commission in attack. Call it fullback, call it five-eighth or whatever... he can even keep wearing the #1 jumper if it makes him happy.
Burt will simply shift out wide after the first play the ball, and still be an attacking option like we're used to on the wing. Gets the best out of both players, and probably saves more tries through Burt's superior positioning.