One could do this after 12 hours of casting time and lots and lots of snow.
So what you are describing is literally preparation for a major showdown being planned by the PC party. In official D&D Adventures, this is likely the for the capstone encounters, so in practice, the Wizard player that has patiently played to reach this power level gets to do this once or twice.
I’m not saying, the spell doesn't have room for abuse, but requires vast planning.
Frankly self duplication is probably the most straightforward use, the fun begins when the party tries to replace a a Monarch, a Gold Dragon, etc....and if the party can pull off something so audacious...then what a fun story that is!