If you could reserve a spot for a pet in the hatchery in your stable, that way all of the pets you don't want don't keep filling you stables while you wait for a certain pet to come of age. (I.e a project pet.)
I know alot of players have tons of eggs, hatchling and such. As well as lots of stable space.

I'm not sure why this would be needed. You can release the pets you don't want from the hatchery, and you can move adolescent pets to your stable at any time so they won't get lost in the shuffle.

If those aren't enough options maybe you could explain more why this would be useful?

Doing that would be a lot of coding for something that already basically exists. In your Hatchery, just set it to automatically release Un-named Adults. Then, simply name (or manually move) the pets you want to keep. All of the others will automatically be removed.

You can do that? How? I don't see any thing like that in my hatchery.

Click the button that says "Hatchery Settings".

*Faceplam* How did I miss that.
Well that solves that, Thanks Krin.