The PPC has been in operation for decades, and there are many Agents and staff from Arda. Now, Sindarin has multiple dialects in-universe, but one or two would be standard.

There would certainly be a ton of loanwords right off the bat, some of them introducing new consonants or reintroducing vanished consonants. Using Salo's book as a guide for consonant mutations:

*Quab, a crustacean from Ahnonay in Mystverse. The base form would be "queb", with the plural "quib".

*Lenition: "i-gweb" (the quab)

*Nasal mutation: "a chweb" ("for a quab")

*Stop mutation: "e chweb" ("from a quab")

*Liquid mutation: "or chweb" ("above a quab")

*Mixed mutation: "en-gweb" ("of the quab")

Now, a Sindarin speaker may get a Gods Must Be Crazy mission. The main character's name starts with a lateral click consonant. So this is guesswork:

*Lenition: "Gxi" (Xi as the direct object of a sentence)

*Nasal mutation: "a Nxhi" ("for Xi"). Note that the click is nasalized as well as aspirated, as nasalization is what happens when a click follows a nasal.

*Stop mutation: "e Xhi" ("from Xi")

*Liquid mutation: "or Xhi" ("above Xi")

*Mixed mutation: "e-Ngxi". ("of the Xi", if the Suethor forgets the apostrophe in "Xi's" and one doppelgänger in particular needs to be singled out.)

Looking at the "ch" in "chair", I gather Sindarin would modify that to /s/?