It would be cool to see the drum corps of the guards added, with snares, flutes and buglers. It would also be cool to see bagpipes (scots/irish guards) as well as the scottish style drum corps. (scottish snares, tenors, basses).
It would also be cool to have a drum major who can control the band and perform mace drill.
you could also have new uniforms. the fleur de lis patterns for the drummers, including a gold variant for the drum major, as well as irish/scottish regimental dress for the pipers. a state dress for drum majors could be included (the one used for trooping the colour)