I suspect it would be a relatively easy swap, but I have not BTDT, so hopefully one of our wheel gurus will pipe up.
The wheel and tire sizes are the same on the 749 and my S4, and the 999 has a 190 rear tire vs. my 180.
I don't notice any lack of "flickability" on my bike. But I can't drag the pegs or other hardware, so...........some others may think different.