I am someone sympathetic to the SSPX and I attend masses at an SSPX chapel on occasion.
I think there are two different approaches to the problem clashing here just as they clashed in 1988. The SSPX wants to enter into deep discussions and have the fruits be formal Papal documents conforming VCII to Tradition before the SSPX enters. The Vatican/ Pope are already slammed busy and are not in the least interested in long drawn out doctrinal discussions with the SSPX. Rome wants a practical solution to this problem as soon as possible and under Benedict is bending over backwards to make that happen.
Bishop Fellay had previously laid down three pre-conditions for reconciliation. The first was freeing of the TLM. The Pope has done this and also freed all of the Trad sacraments and breviary, something even Bishop Fellay was surprised and pleased with. So that is accomplished.
The next pre-condition was the lifting of the excommunications. It is amazing to me that the Pope is apparently going in the order laid out by Bp. Fellay. In their last meeting He had said the excommunications would be taken care of with regularization. But now, I think the Pope is going step by step. He is ready to lift the excommunications and has laid out the 5 bare minimum assurances he would need to do so.
The SSPX accepting these 5 conditions tells the world that the things all the neo-cons have been saying all of these years about the SSPX is false. That they are not their own Church, that they recognize the Pope, etc.
The only condition I see as potentially problematic for them is #3:
3. A commitment to avoid the pretense of a Magisterium superior to the Holy Father and to not put forward the Fraternity [SSPX] in opposition to the Church.
I think the Vatican made these conditions ambiguous to help an agreement take place. But the SSPX hates ambiguity and will want to define things. If so why not define the statement in your response and then agree to it. Put the ball in Rome's court.
In response to this I would start by stating we accept the authentic magisterium of the Pope in all things that accord with Tradition. Since the Pope thinks everything he is saying is in accord with Tradition it shouldn't be a problem.
The point is, the SSPX can agree to these things in principle and wiggle around with their understanding.
Rome is not looking to mess over the SSPX here. I think Benedict wants them IN, and wants the bare minimum from them.
I think the SSPX risks slowly fading into irrelevancy if they don't take the offer and then work as a force for change in the Church. The Pope wants Trad allies in the Church.
This is a huge crossroads in Church history. I pray it turns out for the best!