In contrast with the authors of MM—who deny that the imperfect obedience of OT saints can typify the perfect obedience of Christ (MM 130)—many Reformed commentators taught this very thing. I am no expert on 17th century Reformed literature, but I was able to find the following quotes just by searching Google Books.
In his dissertation, Why Heaven Kissed Earth: The Christology of the Puritan Reformed Orthodox Theologian, Thomas Goodwin (1600–1680) [RHT 13; V&R, 2010], Mark Jones explains that
Goodwin argues that the eminent Old Testament saints were types of Jesus Christ .... Adam, Noah, Melchizedek, Joseph, Moses, Samson, David, and Solomon, for example, were all types of Jesus Christ (p. 93).
But how could sinful OT saints be types of Christ? In his treatise, Of Christ the Mediator, Goodwin explains:
The general rule which the apostles went by, and which the Jews themselves assented unto, and their teachers taught them, was, that whatever eminent and extraordinary excellency was found in any of their ancestors renowned in the Old Testament, or in the ceremonial law, that all such foresignified the Messiah to come, as the perfection and centre of them (Works of Goodwin, ed. Nichol, vol. 5, p. 150).
Or consider Thomas Taylor (1576–1633), an English Puritan who remained within the Church of England. He wrote a treatise titled, Christ Revealed, or The Old Testament explained: A treatise of the types and shadowes of our Saviour contained throughout the whole Scripture (1635). Taylor subdivides the types of Christ into holy persons and holy things. Under holy persons, he includes the following as types of Christ: Adam, Noah, Melchizedek, Isaac, Joseph, Moses, Joshua, Samson, Solomon, Jonah, and others.
I have not read the whole treatise, but I looked at his treatment of Noah. Taylor suggests that Noah was a type of Christ in seven ways. Relevant to our discussion here is the second way that Noah was a type of Christ. Quoting Gen 6:9 (“Noah was a just man and perfect in his generations, and Noah walked with God” [KJV]), Taylor sees this similarity between Noah and Christ: “Both are said to be just and perfect; both said to walke with God.” However, there are differences between Noah’s righteousness and Christ’s, including the fact that “Noah was perfect but in part: Christ perfectly perfect” (pp. 10-11; Early English Books Online, via PRDL).
Samuel Mather (1626–1671) was a Puritan of the Independent variety. He was the older brother of Increase Mather (the father of Cotton Mather). For a time he served as chaplain of Magdalen College, Oxford, under the presidency of Thomas Goodwin. In a treatise titled, The Gospel of the Old Testament: an explanation of the types and figures by which Christ was exhibited under the legal dispensation, he wrote:
Inasmuch as the holiest had their sins, we have further to observe, that they [OT saints] were not types of Christ in regard to their sinful failings, but only in their graces and excellences (p. 82 in the 1834 edition).
John Brown (1784–1858), grandson of John Brown of Haddington (1722–1787), was a minister and professor of exegetical theology in the Scottish Secession church. He wrote a book titled, The Sufferings and Glories of the Messiah (1853), which contained a detailed exegesis of Psalm 18 and Isaiah 53. He argued that Psalm 18 ought to be interpreted as a Messianic Psalm right along with Psalms 2, 16, 22, 40, and 110. He believed that in Psalm 18 “a greater than David is here—that, so far as the subject of the psalm is concerned, David is not here at all, except, it may be, in the way of allusive illustration” (p. 25). When he came to verses 20-24, he interpreted them as referring typologically to the merit of Christ:
In the fourth section of this Messianic psalm ... we find the beloved Servant of Jehovah, delivered from all his enemies and the power of the grave, representing, in his solemn thanksgiving, his deliverance and exaltation as the expression of Jehovah’s entire satisfaction with his conduct, and as the merited reward of his having become obedient—obedient even to the death .... “The Lord rewarded me according to my righteousness; according to the cleanness of my hands hath he recompensed me ...” [Ps 18:20ff]. The words before us are an acknowledgment, on the part of the delivered and rewarded Messiah, of the righteousness of Jehovah in his deliverance and reward. The general idea is,—These wonderful works of Jehovah, which have just been commemorated, are the merited expression of his entire righteous approbation of, and most complacent holy delight in, his humbled and suffering Servant’s person and work (pp. 97-98, emphasis added).
John Brown has a footnote in which he quotes George Horne (1730–1792). Horne was a bishop in the Church of England who wrote A Commentary on the Book of Psalms (1771) that was widely influential in its time and in the subsequent century. Commenting on Psalm 18:20-24, Horne wrote:
Commentators have been much perplexed to account for these unlimited claims to righteousness made by David .... But if the Psalm be prophetical, and sung by the victorious monarch in the person of king Messiah, then do the verses now before us no less exactly than beautifully delineate that all-perfect righteousness wrought by the Redeemer, in consequence of which, he obtained deliverance for himself and his people. For “his” righteousness’ sake Jehovah was well pleased, and rewarded with everlasting felicity the unspotted purity of his works (p. 86).
I have no doubt that further research would turn up more quotes along these lines, but these are enough to provide a general idea. Reformed commentators do not seem to have any reluctance in seeing the imperfect obedience of certain OT saints as typological of the meritorious obedience of Christ. If we readily recognize the imperfect OT sacrifices as types of Christ’s passive obedience, why should there be any problem seeing the flawed obedience of certain OT saints as typological of Christ’s active obedience? I am not aware of any Reformed theologians who share the restrictive view of the authors of MM that imperfect obedience cannot typify perfect obedience. To the contrary, with just a little Internet searching (in English, not even trying Latin) it was not hard to find Reformed theologians and exegetes who took the opposite view. As Samuel Mather said, the OT saints “were not types of Christ in regard to their sinful failings, but only in their graces and excellences.”