The UDT was the first cooker I ever built myself. I stumbled upon the UDS concept on the internet 2 years later, and wondered whether my tandoor could be used to cook other types of 'cue. The basic issue is that a tandoor is supposed to run b@lls-to-the-wall hot... no scope really for temp regulation. I guess you could regulate temperature by building a tandoor with a bottom intake that can be sealed, and a top that can be sealed. At that point you're basically talking about a ceramic cooker and may as well look at a BGE, Kamado Joe, Primo etc, which will be more versatile ( with some accessories).
But for discussion sake, there's nothing to stop one from skewering a steak on a 40" seekh and searing it in the tandoor. I've thought about doing that myself