In RC thinking, there are two movements in the gospel. There is the movement of God downward in Jesus Christ - the incarnation and the cross - and there is the movement of humanity upward. These are two separate things, although the former is to be considered prior. (Whether its priority can be maintained in practice must be doubted). In terms of salvation, this is Roman thought precisely - God makes a move, we make a move. Grace, then free will. In the thinking about Mary, this shows very clearly. God makes a move towards the incarnation; Mary agrees with this move, and thus makes its completion possible. Human co-operation is vital in the Roman system, and the Roman Mary shows it.
Of course, if you believe this there must be some sort of merit that accrues to the human who co-operates. In RC thinking, this merit is found within the church as the institution which co-operates with God. The church is to be thought of as God's kingdom on earth - literally. Here is humanity exalted. No surprise, then, that Mary - the symbol of the church - is enthroned in heaven.
The problem at the most fundamental level seems to be that God simply does too little in the RC system. God comes down in Jesus, but he does not in himself raise humanity up. That corresponding movement must be represented by another figure, Mary, who stands for the institution of the church. In that case, isn't the church simply humanity raising itself - albeit in response to God's summons and in some way through his enabling?
We must instead see the cross and the resurrection together. In Jesus, God is humbled and humanity is raised. He does it all. If we hold to that, Mary can have her proper place of honour - as one who said 'yes' to God. And isn't that a better understanding of the church overall?