So, when we ask each other to pray for us (mediate), we are blessing each other?
Firstly, when we pray for each other, we are doing it as the spiritual bride of Christ, in one Spirit, that is, the body of Christ. So in this regard we are not mediating on each other's behalf, rather as one body in Christ, as it is written, where 2 or more are gathered in the Lord's name, we are petitioning our intentions through prayers, to the one mediator who is Christ.
Secondly, we are not blessing one another through our power, when we pray for others. Rather we are again petitioning to the one shepherd Christ Jesus to bless certain members within the body, so to fulfill the Lord's will.
Thirdly and lastly, the word bless can be used also to show high regard to one who is blessed, meaning Barack, which implies that we are putting the pride we have for the Lord, on display through our hearts. So when I say "blessed are you my Father, you alone know all things, blessed is your name forever!", this implies a Semitic form of supplication with the intent to glorify God.
Mary falls under the third usage of the word blessed, where we are glorifying God through his servant Mary.
We are the temple and Holy instruments within his Holy Temple and so we are glorifying the works of the Lord through members of his body.
One Old Testament prophet summed it up poetically as follows:
Isaiah 8:18
Here am I, and the children the LORD has given me. We are signs and symbols in Israel from the LORD Almighty, who dwells on Mount Zion.
Now, allow me to contextualise this statement according to the New Testament believers.
Here we are as the spiritual bride of Christ, and the children like apostles, Mary and all the saints the Lord has given us. We of the body of Christ are signs and symbols in Christ's church from the Lord God Almighty, who dwells in his Holy Temple.
To bless Mary is to glorify God. In fact to bless each other who do the Lord's marvellous works, we are glorifying God as we are all instruments, signs and symbols of his Holy works.
If we bless one another today, then we do not differentiate between the present and the departed members of Christ's body, who also glorify God, even though they are not around to do it themselves. So that leaves his present members to glorify God from Abraham down to the last member of his body who the sovereign Lord puts his marvellous works on display.
As Jesus said I go to my Father and if you ask in my name, greater works of the Father will manifest through you.
Now whether departed or present all are counted as living stones and if we nit pick who we want to bless in that regard, we are playing favouritism and not sincere in our praise of God.
Do we want to show insincerity to God by picking and choosing who we want to bless?
I don't think so!