But they waited in the Limbo of the Fathers because they could not have justification itself until Christ applied His Passion to them.
This is theologically erroneous. That's like saying the Blessed Virgin wasn't truly justified until after the Passion. It's like positing something other than sanctifying grace justified those under the old dispensation.
No, the Blessed Virgin Mary was an exception, in the sense that She had the fruits of Our Lord's Passion applied to Her beforehand. Read the Council of Trent's decree on justification, which clearly distinguishes between the subjective dispositions necessary for justification and the "justification itself" which comes AFTERWARDS as a result of the application of Our Lord's Passion by Baptism.
But to address the original point, it remains true that they were and are considered "martyrs" for Jesus Christ by the Church. As such, it follows that there can be infant martyrs after His Passion as well. It seems strange that I would have to say this.
Yes, they were martyrs, but their martyrdom wasn't the cause of their justification, i.e. they were not saved by BoB. They were saved by being in a state of pre-justification per the old dispensation. Even the Holy Innocents were hanging out in the Limbo of the Fathers until Our Lord's Passion was applied to them. Why? Because, DESPITE their martyrdom, they were not yet justified. Otherwise, the Holy Innocents would have gone straight to heaven. But they didn't. Which proves my point.
And this would raise other issues if they were saved by this martyrdom, because then you're saying that BoB works
ex opere operato even in those who have not reached the age of reason, i.e. you'd be saying that BoB is in fact a Sacrament, which it is not.
So, no, Caminus, YOUR position is theologically erroneous. To say that sanctifying grace somehow justifies (and can even exist) apart from the free-grace unmerited application of Christ's merits by Baptism contradicts the Council of Trent's decree on justification. You're almost implying that people can earn justification by getting into a state of sanctification--which is PRECISELY why I reject BoB and BoD.