Hilastrion as either propitiation or expiation

 "[Jesus] whom God put forward as an expiation [hilastrion] by his blood, to be received by faith." RSV  Romans 3.25a

Could hilastrion have a double meaning like hagorazo?

The two meanings are not equal but 2 separate stages.  Hilastrion could be propitiation or expiation. The former is the basis for the latter.

Just like Hagorazo could be "purchase" or "taken possession of."  Everyone is purchased, but only believers have been taken possession of by God.  

2 Peter 2.1: "...false teachers among you, who will secretly bring in destructive heresies, even denying the Lord who bought [hagorazo] them, and bring on themselves swift destruction." NKJ

Revelation 5.9 "For You were slain,

And have redeemed [hagorazo] us to God by Your blood
Out of every tribe and tongue and people and nation,"

Romans 3.25 could mean "expiation" instead of "propitiation."  Expiation is through faith, because of the Propitiation by the death ("blood") of Christ.   

1 John 2.2 "And He Himself is the propitiation [hilastrion] for our sins, and not for ours only but also for the whole world."

Propitiation is the "satisfaction" of divine justice for all sin of all people, while the expiation of sins or the "remission" of sins is through faith--only true for those who believe.

The death of Christ is the propitiation for sin by which one receives expiation/ remission of sins by believing in Jesus as the Christ (son of God) who saves them by his propitiation from their sin (expiation/ remission of sins, justification, and new birth).