The resurrection of those in Christ
Briefly, the assumption is that resurrection belongs fundamentally to the new creation: it constitutes for the individual the final abandonment of this creation and entry into a radically new ontology in which there is no more sin and death. Any resurrection prior to that final renewal of heaven and earth is ontologically misplaced - it anticipates something that has not yet happened. But belief in resurrection develops in the first place, biblically, not from reflection on the universal condition of death but from the conviction, on the one hand, that God would renew corporate Israel through judgment (Ezek 37:11-14; Hos. 6:1-2), and on the other, that he would not abandon the individual righteous to death (Dan. 12:2-3).
So the argument is that in the New Testament resurrection is both the vindication of the true Israel that suffers and an anticipation of new creation - it may even be that it is precisely the radical ontological transformation of Jesus that gives rise to the hope that all creation will ultimately be transformed around the Lamb of God. Those who suffer out of obedience to YHWH - Christ the first-fruits and those in him - are raised in the context of that eschatological crisis to share in the kingdom that is given to the Son of man. But where are those resurrected bodies to go? They belong to a new ontology that does not yet exist, so they ‘go to heaven’ to reign at the right hand of God, until the reign of God no longer needs to be exercised through the Son who suffered, died and was vindicated. Their existence in heaven is presumably as ‘bodily’ as Christ’s existence in the heaven is bodily.
Does it matter that the resurrection of the martyrs in conjunction with the eschatological crisis of transition was not physically seen? For the dead in Christ to share in the vindication of the Son of man, is it necessary for them to be raised bodily from their tombs and literally transported through the air to join Christ on the clouds of heaven? I just don’t think the language of prophecy requires that, but clearly there is scope for disagreement, and I’m not sure we can solve the problems on exegetical grounds. Anyway, I don’t see a contradiction between the idea of an unseen resurrection of the martyrs and their continuing bodily existence at the right hand of God, for the reason that Christ’s own continuing bodily existence is also unseen.