In the very least, I believe that baptism of desire is possible for catechumens, as per Pope St. Pius V's Ex Omnibus Afflictionibus (nn. 31-33, 43, 70.).
http://onetruecatholicfaith.com/Roman-Catholic-Dogma.php?id=26&title=Denzinger+1001+-+1100&page=2
The fact that certain misinformed baptism of desire teachers continue to attempt to quote the Errors of Michael Du Bay, simply
shows their lack of evidence for “baptism of desire.”
Errors of Michael Du Bay, Condemned by St. Pius V in “Ex omnibus
afflictionibus,” Oct. 1, 1567: “31. Perfect and sincere charity, which is from a
‘pure heart and good conscience and a faith not feigned’ [1 Tim. 1:5], can be in
catechumens as well as in penitents without the remissions of sins.”437 ‐
Condemned
Errors of Michael Du Bay, Condemned by St. Pius V in “Ex omnibus
afflictionibus,” Oct. 1, 1567: “33. A catechumen lives justly and rightly and
holily, and observes the commandments of God, and fulfills the law through
charity, which is only received in the laver of baptism, before the remission of
sins has been obtained.”438 ‐ Condemned
Michael Du Bay’s propositions above are condemned because they assert that perfect charity can be in catechumens and penitents without the remission of sins. (Note: this says nothing one way or the other about whether or not perfect charity can be in catechumens with the remission of sins.) Du Bay’s propositions above are false because one cannot have perfect charity without the remission of sins.
Pope Paul III, Council of Trent, Session 6, Chap. 7 on Justification, ex cathedra:
“Justification … is not merely remission of sins, but also the sanctification and
renewal of the interior man… Hence man through Jesus Christ, into whom he is
ingrafted, receives in the said justification together with the remission of sins all
these gifts infused at the same time: faith, hope and charity.”
Faith, hope, charity and the remission of sins are inseparable in a justified person. Thus, Michael Du Bay was rightly condemned for his false statement that catechumens and penitents can have perfect charity without the remission of sins. His assertion contradicts Catholic teaching. And when a pope condemns propositions like the false propositions of Michael Du Bay, he condemns the entire proposition as such. In condemning such an error, no assertion is made positively or negatively about either part of the statement, nor is any assertion made, positively or negatively, about whether catechumens can have remission of sins with perfect charity, which is not the topic of Michael
Du Bay’s statement.
If you want to believe in BOD of the catechumen, there are saints quotes that support that theory, but the condemnation of Du Bay is not one of them.