I love this idea, but why not add a propane grill as well? Every non-restaurant grill I've seen has been propane.A grill. Have had several ideas for this. Don't even attempt to begin to comprehend why I have thought this indepth about grilling in minecraft though. Associated items such as different types of woods, possibly a kiln to make drywood for wood that changes the output of food cooked by the grill with that wood or charcoal of that wood etc etc. Associated food types as well.
First: Obviously just a basic block, maybe some netherrack and a flint and steel in the recipes with cobble/bricks/w.e
Second type: Multiblock. GUI-less for putting food in but perhaps a block in the back for a place to add in the fuel? http://i.imgur.com/3klG7nk.png The iron bars are a bit wonky since they'd need to lay flat like a grill but yea.
Final type: Well since you said you want to build up to the cofh api... Why not an electric grill? :3 Not much in the way of ideas on that one.
Anyway thought this might be fun and a good few things to learn coding wise.
This poses a glaring flaw, however: how do I get propane? Well, irl, it is a byproduct of refining crude oil into gasoline. Maybe if BC is installed, use its oil, bit if it's not, gen your own oil. Then you could add a multiblock refinery to separate propane from gasoline. This has the bonus(?) of giving you gasoline to use how you see fit.