I make my own liver jerky, it's the only thing he really loves, it stinks but the alternative products made only from real ingredients are just too expensive. Keep meaning to make liver cake but just haven't got around to it. Good luck.
I buy all my dog treats online, as long as they are natural, grain free etc, reasonably priced I would give them a go.
As long as you know that there is more to it than just baking in the kitchen.
For a start do you know if you need to produce them in a stainless steel commercial kitchen, will you need insurance if someones dog chokes or gets sick from eating them? You will need correct labelling ingredients etc. Pet Food health and safety rules are just as strict as peoples.