Or, more of them, I guess? I feel so bad for the Ticks and Tick-Tocks I inevitably kill to fight my way down to the clock tower floors that I'd rather just adopt one instead... Though that could take some work, both coding and in editing sprites (though it wouldn't be too hard to give a Tick/-Tock a smiling face), I'm sure it'd be popular as a concept with other users. Some of these monsters are just outright adorable. It hurts being an adventurer. ;_;
I like the idea but it will be difficult to put in all the mobs people might want...Not to mention having to scroll trough multiple pages of pets in the cash shop to get the one you want. In some versions of the game, there also is the familiar system which lets you do something similiar. You can basically collect any monsters card drop and then summon it. It will attack and have a special effect (like heal hp/mp or increase a stat by 1). Anyways if you want to go trough with this suggestion you should probably make a poll which mobs to make into pets.
That's what I was thinking. Maybe going by tiers of popularity so you get Pigs, Slimes, Mushrooms, etc. out of the way and then work down from there. The familiar system sounds neat, but... it's not exactly what I was looking for. [edit] Poll's up! Feel free to pitch your voice.