We already have lykos, more breedable dog/wolf like creatures are not needed. Could always make or commision a custom skin of those other creatures and apply it to a lykos. Rainbow jars arnt that hard to come by for a few pets to have skins.
Baskilisk is already cockatrice, and someplace coding the cockatrice is called baskilisk. And, custom skins are great for adding new looks to a pet.
Swans, pheonix, can be made to custom skins. Someone has asked about pheonix custom skin, the responce from angel was "phoenix skin is fine. We don't plan to introduce phoenix as a breedable species because this creature is too specific, and it's not specific anatomy - it's, ehm, material :)"
As Seelenblut said, keeping a humanoid would be strange. Even if its made unintelligent, then its like keeping a mentally retarded person as a pet and breeding them. It just doesnt feel right. Even if just having a humanoid head. If just hinting at a human face like the shape i think it would be alright, but actual human heads and humanoids just dont feel right to me.
Quilen/kirin can be made to custom skins, i made a kirin skin a long while ago for unicorns thats available now.I should propably make an update of it.
All the custom skins is assuming you just want the look. Adding in a species takes soooo many hours and a lot of coding, a lot. Enough to make someone insane. Making a custom skin would atleast be even ground?
You should provide genes and images of all the creatures. As i think a sticky said, just saying the name isnt enough.
The one you suggested that I would like to have breedable and not just a skin would be the manticore (without human face). Need some genes worked out and some images though, and im pretty sure someone has suggested it before. Maybe colaberate with them?
Don't get discouraged, getting feed back helps weed out ideas and add onto good ones. I could work on the manticore one with you, if you are serious about doing hours to add a new species.
I would like to see Angel respond to your ideas, see which ones would be best to add to the game.