Yes, it shouldn't be very hard at all, however, there are
five ways for someone to obtain a pet nowadays, and modifications will have to be made in all of those places. I'll put it on my to-do list right after dinner.
I'll create a new mod thread for it. At the same time I'm also going to include a 'birthday' value, so you can display when a pet was born and/or how old it is, if you want, too.