If the SSPX places themselves under the direct control of the Pope, they must needs compromise on something because this pope still lauds Vatican II. The pope will have a say in something or another that will not be pleasing to many in the SSPX.
Even if Benedict XVI is completely and absolutely amenable to what the SSPX faithful wish, and gives them an irrefragable and definite authorization to do what they deem fit, one problem remains:
The N.O. does not seem to understand the primacy and infallibility of the Roman Pontiff as the Vatican Council defined it. They have this "collegiality" notion that the Roman Pontiff, together with
the aggregate of the Bishops, rules and guides the Church of Christ: to what degree individual clergymen may espouse this at the theoretical level is a moot point, because it is evident that in the practical order this novel ecclesiology is the norm that determines the behavior of the N.O. bishops at large. The N.O. bishops will do as they please, no matter what Benedict may say: and it is clear that the N.O. bishops at large have an animosity against anything resembling traditional Catholicism.
I do not think that the same N.O. bishops who have opposed any concession on the part of the Vatican to what the SSPX has to say would allow the SSPX to function as it has done independently.
The 'collegiality" notion is even more disastrous because the bishops' autocratic spirit has rubbed off on the priests at the parochial level. Ever since I could remember, my former pastor at the N.O. did and said whatever he pleased at the N.O. services, so that the leaflets that were passed out were basically useless. Many people have told me they have noticed similar behavior.
Speaking of the N.O. predicament at the parochial level, the official translations of the N.O. rites may have become more conservative, but there is still a culture of married deacons, female altar servers, lay "Eucharistic ministers," &c., that makes any substantial attempt to return to the teachings of the Tridentine Council self-defeating. Words like "sacrifice" may have no meaning to one who has been indoctrinated in the N.O.'s novel methodology and orientation of catechizing. This is at least my observation from what I have seen at the local N.O. services in my area.