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On the account of Jesus' encounter with Nathanael, this is written:

Joh 1:47  Jesus saw Nathanael coming toward him and said of him, “Behold, an Israelite indeed, in whom there is no deceit!” (ESV)

Εἴδεν ὁ Ἰησοῦς τὸν Ναθαναὴλ ἐρχόμενον πρὸς αὐτόν, καὶ λέγει περὶ αὐτοῦ, Ἴδε ἀληθῶς Ἰσραηλίτης, ἐν ᾧ δόλος οὐκ ἔστιν. (MT)

Can the statement utilizing the word δόλος here mean something like, "you are a pure-blooded Israelite, without stain (of another blood)", or does it only, as in most commentaries, mean that Nathanael has no deceit "in his mouth" (i.e. not a deceitful person)?

There doesn’t seem to be much variation in the meaning of δόλος. If you want to express it in a different way, Jesus was saying Nathanial’s religious service as an Israelite was genuine, without hypocrisy.

δόλος, ου, ὁ (…) deceit, cunning, treachery … ἐν ᾧ δ. οὐκ ἔστιν in whom there is nothing false

Arndt, W., Gingrich, F. W., Danker, F. W., & Bauer, W. (1979). A Greek-English lexicon of the New Testament and other early Christian literature : a translation and adaption of the fourth revised and augmented edition of Walter Bauer’s Griechisch-deutsches Worterbuch zu den Schrift en des Neuen Testaments und der ubrigen urchristlichen Literatur (p. 203). Chicago: University of Chicago Press.

88.154 δολιόω; δόλος, ου m: to deceive by using trickery and falsehood—‘to deceive, to trick into, treachery.’
δολιόω: ταῖς γλώσσαις αὐτῶν ἐδολιοῦσαν ‘with their tongues they keep deceiving’ Ro 3:13.
δόλος: συνεβουλεύσαντο ἵνα τὸν Ἰησοῦν δόλῳ κρατήσωσιν ‘they made plans to arrest Jesus by means of treachery’ Mt 26:4.

Louw, J. P., & Nida, E. A. (1996). Greek-English lexicon of the New Testament: based on semantic domains (electronic ed. of the 2nd edition., Vol. 1, p. 758). New York: United Bible Societies.

The Syriac Peshita has ܕ݁ܢܶܟ݂ܠܴܐ :

ܢܟܠܐ, ܢܶܟ݂ܠܴܐ Noun. Gloss: deceit; guilt; trickery; guile; craft.

Kiraz, G. A. (2003). Analytical lexicon of the Syriac New Testament: based on the SEDRA 3 Database of George Anton Kiraz. Bellingham, WA: Logos Bible Software.

The Latin Vulgate has dolus:

dolus, i, m., guile, 2 Co. 12:16; craft, deceit, 1 P. 2:1 ff.

Harden, J. M. (1921). Dictionary of the Vulgate New Testament (p. 39). London; New York: Society of Promoting Christian Knowledge; The Macmillan Co.