Actually Booze Rutherford did give a lesson in this.
Up to the 20's JW preachers were expected to wear frock coats on the podium. Rutherford realised that in order to move with the times less formal attire would appeal to the gophers.
He astonished an audience (I forget where) when he went onto the assembly platform dressed in a lounge suit. The lesson he was teaching - that christians cannot be sanctimonious about their dress. (Ironically in the mid 90s a brother did do the announcements in a (then comeback) frock coat. He was counseled for dressing too worldly!!)
Alas the lesson was lost - lounge suits are now the new sanctimonious garb.
I reckon if it survives long enough, to keep up the appeal to the young (i.e. fundraising healthy) you'll see men giving talks in open neck shirts, or jeans and sweat top. If it keeps cash comin in, why not?
HB (of the we aint evolving new fur class)