Accepted marketing practice is to offer three alternatives as this gives customers a choice and they can make a decision and buy immediately. Offer more alternatives and you make the decision harder and customers are less likely to make an instant decision. Just a thought, not compulsory
From my own perspective I like the idea of indigenous species that gives UK BBQ more of an individual identity. I'd like to see apple for poultry & game, a strong wood such as oak for red meats and maybe cherry as a good all rounder.