You are certainly welcome to opine that pigs can fly too. That doesn’t mean your opinions are credible, especially when you assert equally silly rationales such as an omission by a later condensed version Catechism MUST mean correction of a prior error

. That is just wishful thinking on your part.
Is it erroneous to belive in the limbo of babies also? I do not believe so, while it is not currently taught explicitly in the Catechism it is still acceptable to hold that teaching, it has been omitted but never denied as possible.
The Church has clearly taught that unbaptised babies are in a state of mortal sin and this teaching is much stronger than that of limbo.
If you opine, contrary to the Church, this teaching is actually in error the burden is on you to make a clear case. What you actually need to do is provide a brief and clear theological reason why it cannot be true for you will not find anything so explicit ever asserted by the Magisterium.
The real issue is not that the Church was in error on this point…rather you yourself do not seem to quite understand what it actually means. Possibly because your own understanding of sin is where the mistakeness actually lies. A possibility you seem unwilling to acknowledge.