I have an R6 swingarm out in the garage. Haven't got around to doing anything with it because...
Bear in mind that due to the triangulation of R1/R6 engines (input / output shaft mounted more vertically, meaning the engines were shorter), their swingarms were about longer to compensate. Fitted to the Fazer, they will be about 1.5 inches longer; this will be fine if you spend your time cruising in straight lines but will destroy decent cornering ability.
Better swaps would probably be either the TRX850 or YZF750 swingarms, which are closer to the FZS600 length-wise. I believe RubyRacer has also fitted a FZR 1000 Exup swingarm to his.