Is it at all possible to do this

for example i'm walking along and I bump into a rat now I could just cast a command beast spell but that ends, I want to make it my pet, then be able to name it, have it level with me, etc.

i hope that makes some sense

although if there is a mod that already does this I would greatly appreciate if someone pointed me in the direction of it

Cheers

You could make a series of AI packages and use a scripted spell to add them to the target. Look at the CM Partners base mod. There are several Creature companions in it. And you can load the CM Partners .esm in the CS and just make a spell that adds the necessary pre-made AI packages to the target. Also make sure to add the PlayerFaction to it and reset it's Aggression (18 or so will cause it to attack anything that attacks the Player).

Check out this mod:
http://planetelderscrolls.gamespy.com/View.php?view=OblivionMods.Detail&id=5813

I just tried to add a small, friendly wolf to my private room I created in a Tavern. I assigned it PlayerFaction. In game it ran around wildly, bumping over all small furniture. After a while a Guardian soldier entered the room and slayed it! - Poor wolfie.