Well, first off, the official term (yes, there actually is a word for this) is devolution. There's even a page about it on Bulbapedia; http://bulbapedia.bulbagarden.net/wiki/Devolution
I'd be kinda glad that GameFreak decided to implement devolution in the games, though I'd be kinda pissed if we could never evolve them again. Suppose someone has a female Glalie, and decides they want her to be a Froslass instead? I'd prefer a devolution item that devolves the Pokémon, but lets it keep the moves it had, and allows it to evolve again (provided it's able to meet the requirements- that is to say, as long as it's not something like a level 100 Wynaut that can't level up again).
Question- would your idea allow for a Light Ball to work on a devolved Pikachu? --- Official badass Admin of Team Miror Infinity. I ride a Shadow Scolipede. Top that. http://imageshack.us/a/img202/4572/missingnogif.gif
I wouldn't mind being able to use a Zorua with the stats of a Zoroark at all. I'd personally be fine with this. --- "This isn't the Ask Auntie Pandora Hour!" ~ Pandora, Kid Icarus: Uprising Official Zorua of the Pokemon X / Y boards.