If I was building my own, it would have to have the following:
Smoker
Griddle
Coal & Gas Capable
At least 2 shelves (cooking & warming)
Ability to cook in the rain and not get too wet
Cold storage (Fridge or cool box inbuilt)
Ability to use as a chiminea, or one built in somewhere
I’m sure there are loads of things I haven’t mentioned that are also essential!
I would go sideways, rather than up with a BBQ, as its easier to control the temp, very similar to KonaStoner’s setup, would also be better for smoking food.