Since the greatest pain of the souls in Hell is the deprivation of the Beatific Vision, it would make more sense to put them in the "upper part" of Hell, where the suffering from the fire would be minimum than in Limbo with the infants who have no personal sin.
It sounds strange that those who die with personal and original sin should have a similar fate to those who have only original sin.
Highly speculative talk anyway.
Well, that's the entire point of Ladislausianism, that the martyrs too have all their personal sin washed away. I hold that unbaptized martyrs (catechumens) if there are any such in Limbo, experience even a greater measure of natural happiness than the infants who die without Baptism. Just as the infants realize that they were spared eternal torment by being taken from life early, so too these martyrs realize that they were allowed this state of happiness because they would have been lost had they lived, been baptized, and then lost the faith somehow or died in mortal sin later on down the road. Those catechumens with BoD, however, they may or may not have all their sins remitted by their desire, depending on how perfect it was.
Just as the pain of sense is not monolithic, neither is the pain of desire. Infants who did nothing to lose it suffer no pain of loss, as per St. Thomas. And those, perhaps, who lived in invincible ignorance, feel little or no pain of loss, though they may feel some pain of sense for actual sin. Catholics who had the faith but then died in mortal sin feel more pain of loss. Catholics who had the faith but then lost it or rejected it feel even more. Perhaps Judas feels the most pain of loss of anyone. So just as pain of sense admits of degrees, so does pain of loss.
There may or may not be a "hard" border between Limbo and Hell, as some theologians hold it to be a part of Hell, but the main point is that outside the Kingdom of Heaven there's a continuum from the highest degree of perfect happiness (say, for martyrs) to a high degree (unbaptized infants) to virtuous invincibly ignorant to unvirtuous invincibly ignorant to Judas and the demons. I don't believe that there are 7 levels of hell, but, rather, basically a unique "level" of suffering for every single soul directly proportionate to their degree of sinfulness vs. their degree of natural virtue vs. their culpability with regard to various sins.