Value 6 is not marginal. Once you have an serial verb construction with a motion verb as verb 1, it must be followed by ‘go, come’ etc. As verb 2, and you must use the preposition too. Value 2 is pervasive when the only motion verb is ‘go/come’ etc, value 6 is pervasive when you have both a verb of motion and ‘go/come’ etc.
Source: Winford 2000: 112
Source: Winford 2002: 408