What did you guys think of the ᾧ relative pronoun in v6? NASB renders it "in this you greatly rejoice", which would make its referent φρουρουμένους, ie "you rejoice in your being protected by the power of God".

I prefer that ᾧ refer to God, since the only independent clause in the sentence in vv3-5 is "Εὐλογητὸς ὁ θεὸς καὶ πατὴρ τοῦ κυρίου ἡμῶν Ἰησοῦ Χριστοῦ". On that reading, it would be "Blessed be the God and Father of our Lord Jesus Christ, [a bunch of explanatory support material], in whom you rejoice greatly" (or if you wanted to break it up into two sentences, "In Him you rejoice greatly")

Is there something I'm missing that prefers NASB's reading that you guys see?

I went back and forth for a while about whether to read ἐν ἁγιασμῷ πνεύματος as "in the sanctification of the spirit" (reference; referring to the believer's spirit) or "by sanctification of the Spirit" (source; referring to the HS). Ultimately I opted for the latter, since the emphasis of the salutation is on God's sovereign action and choosing rather than on the action of the believer. It's not until v6 that the believers are "doing" anything, and even then, all they're doing in vv1-12 is rejoicing at God's action in saving them, keeping their inheritance, guarding them, etc.

I found it interesting that Peter places ἐκλεκτοῖς in apposition with παρεπιδήμοις, he identifies them as the "elect" prior to identifying them as "sojourners" in Pontus, Galatia, etc. (a reality which, if Jobes's reconstruction of 1Pet's audience as exiles from Rome is correct, would feel like a much clearer reality of their lived experience), before then going on to explain the circumstances of their being chosen. It's a super strong reframing of them as God's elect > Rome's foreigners (although they are both).