First, Paul VI made absolutely no changes to the actual Tridentine Latin Roman Rite; he simple promulgated a new order of Mass. The Novus Ordo Mass is not an upgrade or modification to the Tridentine Mass. It is a completely brand new rite.
Yes and no. It started out as a modification/replacement of the old rite. But when the sspx kept using the 1962 missal, new-rome said their new missal was just a "different usage of the same rite". It's a new rite, based off an old one. It's not brand new, because not everything changed.
Really, your point is irrelevant. Quo Primum codified the mass and NO ONE is allowed to say a mass using ANY OTHER RITE under pain of sin. Case closed.
Second, if Paul VI was indeed Pope, then he was just exercising his proper authority "when introducing and approving a new rite or modifying those he judged to require modification”. Historical evidence proves this fact. There are many rites out there that the Church has used and approved. Pope Pius XII clearly teaches this in Mediator Dei:
"The Sovereign Pontiff alone enjoys the right to recognize and establish any practice touching the worship of God, to introduce and approve new rites, as also to modify those he judges to require modification.”
I've pointed the above error out to others and I will point it out to you, to give you once chance to have integrity and accept correction.
You are quoting point #58 of Mediator Dei
out of context and this is deceitful. You are basically arguing that the pope can change the mass anytime he wants, with no limits. THIS IS HERESY. The mass is Christ's; it is Divine. There are human elements, which can be changed, but the essense of the sacrifice is from God's hands, which cannot be changed EVER, even by the pope. As Mediator Dei explains in Point#50, which is a mere 8 points before your point 58..
50. The sacred liturgy does, in fact, include divine as well as human elements. The former, instituted as they have been by God, cannot be changed in any way by men. But the human components admit of various modifications, as the needs of the age, circuмstance and the good of souls may require, and as the ecclesiastical hierarchy, under guidance of the Holy Spirit, may have authorized.Again, your argument is wrong. To argue that the pope can change the mass essentially, is to argue that the Church is not of Divine origin.
If Paul VI was indeed Pope, he could promulgate a new Latin rite given that no Pope has an authority higher than another Pope.
And if you think otherwise, that is an indication of a fundamental misunderstanding of the nature of Papal authority.
Paul VI could've changed the law of Quo Primum, but he did not. Yes, he had the authority to issue a revised missal, but he did not. Pope Benedict XVI confirmed that Quo Primum is still in force. Ergo, the 1962 missal, which is a legal revision of Pope St Pius V's missal, is THE MISSAL of the latin church. Paul VI's missal is not allowed to be used without sinning, and is not required to be used.
It's also quite funny (and sad at the same time) that you are comparing authority between popes, yet you've made yourself THE highest authority, by judging the pope himself. Oh the irony!