As much as I hate to say it, I think they should be left as they are now, with the exception of being able to move them into your vault/gallery so they don't clog up the inventory.

That might be a lot of work for them to do something like this that likely wouldn't affect a whole lot of people, and particularly with an item they already made edible so that there's something to do with them when a player has no more pets they want to train.

I also don't support this going higher. I would farm the crap out of them and use them on bigger pets.

You could adopt/make another pet to use your eggs on. Or use them on a pet you already have that is below Tier 4. You clear your inventory and get a free Tier 3/4 pet out of it.

Or adopt a pet, egg it and put it back in the pound. That would make some random person happy when they adopt it. Maybe do it with for a pet with a horrible name and give someone incentive to adopt, rename and make it a battle pet.

Hmmm. I would probably, if I were the game designer, make it so you earned a random egg say, every 100 battles on a specific opponent... And make it so you combine 10 eggs of the same kind into a "better" egg which works on tier 5 pets... And obviously you combine ten of these to make a "betterer" egg which works on tier 6 pets.