I actually wonder if this could be a way to satisfy another thread I just read about how pet level affects the score.viewtopic.php?f=4&t=4995
They are suggesting a bonus be added for leveling pets to 25 since it takes much more effort to level a pet from 24-25 than it does to level a pet from 1-2. The current system dosn't factor in that extra effort.
The problem brought up by site officers, though, is that this site was created with the emphasis on collecting, not battling, and they would prefer to keep that emphasis.
Using the achievement system, though, could potentially give both collecting and battling equal sway without the potential for abuse on either side.