It seems like we know everything there is to know already about Dwight. The beet farm would really even be a new setting for him. Frasier worked because we really didn't know anything about his life on Cheers other than Lilith and the psychologist job. They were all completely new characters and Seattle was a completely new setting. If they wanted an Office spinoff, they'd be better off going with someone who they could have a clean slate with. Like I said earlier, Creed is the most obscure (and wow could they have some fun with that), but other than that, they might have some decent material for someone like Stanley or Kevin.