It is interesting (although I might part company with some of Nave's wording) that there seems to be relational completion which comes from repentance and forgiveness. Repentance without forgiveness still reflects a disrupted relationship - one that cannot properly heal and grow. Although this goes a bit beyond Nave's specific exegesis, there is no mention of the ramifications of the failure to forgive someone who is repentant. And his overall thesis supports the notion that it is for the edification of the community that this process be taken seriously.
Earlier in his discussion of Luke-Acts, Nave mentions that the entire notion of forgiveness as presented in the Gospel is directed toward the creation of a radically new community of God's people - at which point N. T. Wright would correctly remind us that this community/church is the new temple which Jesus was restoring (see Nave, 169). Failure to participate in the proper modes of repentance and forgiveness tears down that which is being built, and keeps the kingdom from moving forward in its goal of the restoration of God's people. Thus, it might be said that repentance begins and forgiveness completes the work of salvation and restoration.
Further notes: 1) the focus of repentance is both before God and interpersonally; 2) those who repent before God find immediate forgiveness and thus immediate participation in the restoration community; 3) the act of forgiveness disrupts interpersonal relationships and often hinders the realization of the kingdom; 4) the lack of receiving interpersonal forgiveness by a repentant individual does not hinder their participation in the kingdom.