We provide the link to the leaked document for those who read French. The substance of the letter recalls the recent meetings in Rome; the new changes suggested by some in the Curia during the June meetings, Bishop Fellay's response to hold back and take a summary view at the General Chapter, and finally a few absolute points that the SSPX feel must be enshrined in any canonical deal with Rome.
From my perspective, there is nothing new here (e.g. maintaining liturgical practice according to the older rites). Gratifying is the emphasis of the Society to maintain its structure and activities directly under the Pope, by-passing interference from the local Ordinary. Obviously, the activities of the Society would be contained within the local church or chapel - but the key would be that the Society would continue as is, under the Pope.
Point 1, could be the only difficult point for some; whereby it focuses on Vatican II. This could be explained in a number of ways, as has been proposed by scholars such as Msgr. Bux. In essence, it would be to "agree to disagree" on a number of points (as written about by Fr. Lamont) discussed during the Council that had different points of emphasis prior to the Council.
Practice your French, pray for a resolution...