Referred to by the authors as the "pending" sailors, these senshi don't transform in the first series because they don't exist
yet. After all, when the original Sailor Neopets first fought the Chaos Faerie, Meridell and Maraqua and a dozen other worlds had yet to be discovered. Ixis, Draiks, Koi, and over a dozen other species had not been found. Thus, there was no Sailor Ixi or Sailor Koi among the original sailors to pass her powers on to a grandchild.
When a crisis comes and the current group of sailors find themselves in need of help, they will inaugurate new people to fill the positions - trusted friends and former allies (many of whom appear on the Series I Other Characters
page), whom they will recommend to the Faerie Queen. Fyora will give them Sailor Neopet power just as her mother gave the originals power 75 years ago.