How does phonotactic knowledge influence the path taken by language change? As is often the case, the null hypothesis seems to be simply that it doesn’t. Perhaps speakers have projected a phonotactic constraint C into the grammar of Old English, but that doesn’t necessarily mean that Middle English will conform to C, or even that Middle English won’t freely borrow words that flagrantly violate C.

One case comes from the history of English. As is well known, modern English /ʃ/ descends from Old English sk; modern instances of word-initial sk are mostly borrowed from Dutch (e.g., skipper) or Norse (e.g., ski); sky was borrowed from an Old Norse word meaning ‘cloud’ (which tells you a lot about the weather in the Danelaw). Furthermore, Old English forbids super-heavy long vowel-consonant cluster rimes. Because the one major source for /ʃ/ is sk, and because a word-final long vowel followed by sk was unheard of, V̄ʃ# was rare in Middle English and word-final sequences of tense vowels followed by [ʃ] are still rare in Modern English (Iverson & Salmons 2005). Of course there are exceptions, but according to Iverson & Salmons, they tend to:

• be markedly foreign (e.g., cartouche),
• to be proper names (e.g., LaRouche),
• or to convey an “affective, onomatopoeic quality” (e.g., sheesh, woosh).

However, it is reasonably clear that all of these were added during the Middle or Modern period. Clearly, this constraint, which is still statistically robust (Gorman 2014:85), did not prevent speakers from borrowing and coining exceptions to it. However, it is hard to  rule out any historical effect of the constraint: perhaps there would be more Modern English V̄ʃ# words otherwise.

Another case of interest comes from Latin. As is well known Old Latin went through a near-exceptionless “Neogrammarian” sound change, a “primary split” or “conditioned merge” of intervocalic s with r. (The terminus ante quem, i.e., the latest possible date, for the actuation of this change is the 4th c. BCE.) This change had the effect of temporarily eliminating all traces of intervocalic s in late Old Latin (Gorman 2014b). From this fact, one might posit that speakers of this era of Latin might project a *VsV constraint. And, one might posit that this would prevent subsequent sound changes from reintroducing intervocalic s. But this is clearly not the case: in the 1st c. BCE, degemination of ss after diphthongs and long monophthongs reintroduced intervocalic s (e.g., caussa > classical causa ’cause’). It is also clear that loanwords with intervocalic s were freely borrowed, and with the exception of the very early Greek borrowing tūs-tūris ‘incense’, none of them were adapted in any way to conform to a putative *VsV constraint:

(1) Greek loanwords: ambrosia ‘id.’, *asōtus ‘libertine’ (acc.sg. asōtum), basis ‘pedestal’, basilica ‘public hall’, casia ‘cinnamon’ (cf. cassia), cerasus ‘cherry’, gausapa ‘woolen cloth’, lasanum ‘cooking utensil’, nausea ‘id.’, pausa ‘pause’, philosophus ‘philosopher’, poēsis ‘poetry’, sarīsa ‘lance’, seselis ‘seseli’
(2) Celtic loanwords: gaesī ‘javelins’, omāsum ‘tripe’
(3) Germanic loanwords: glaesum ‘amber’, bisōntes ‘wild oxen’

References

Gorman, K. 2014a. A program for phonotactic theory. In Proceedings of the 47th Annual Meeting of the Chicago Linguistic Society, pages 79-93.
Gorman, K. 2014b. Exceptions to rhotacism, In Proceedings of the 48th Annual Meeting of the Chicago Linguistic Society, pages 279-293.
Iverson, G. K. and Salmons, J. C. 2005. Filling the gap: English tense vowel plus final
/š/. Journal of English Linguistics 33: 1-15.