Nobody has ever shown any interest in challenging swift or the legend tag for that matter. If someone really was interested in it I wouldn't be against giving them a way to obtain it.
I do like that idea of master<grandmaster<legend
I'll be interested in the legend / grandmaster tag if its fixed on the speed I play, even faster. If my opponent is allowed to pick maps on fastest speed I don't have any chance.
I never considered Legend tag because I thought Swift would just have all the settings in fastest.