St. Thomas Aquinas disagrees, as do nearly all pre-Vatican II Catholic theologians.

Above, I used the following example: An ecuмenical council had defined that the Holy Spirit proceeds from the Father. But that does neither define nor imply that the Holy Spirit does not proceed from the Son, too.

The initial point that needs to be made in this discussion is that the infallibility of canonisations is not taught by the magisterium of the Church. Belief in their infallibility is not therefore required of Catholics. This point is agreed on by theologians, as can be illustrated by the teaching of a standard manual of theology; van Noort, Castelot and Murphy's Dogmatic Theology vol. II: Christ's Church (Cork: Mercier Press, 1958). These authors follow the traditional and very important practice of attaching a theological note to every thesis that they advance. These notes specify the degree of authority possessed by each thesis, and the corresponding obligation to believe that is laid upon Catholics. The highest note is 'de fide': it belongs to propositions that must be believed with the assent of theological faith, and that cannot be knowingly and pertinaciously rejected without committing the sin of heresy. The lowest note is 'sententia communis', which, as Ludwig Ott states, means 'doctrine which in itself belongs to the field of free opinions, but which is accepted by theologians generally' (Ludwig Ott, Fundamentals of Catholic Dogma, 6th ed. (St. Louis, Mo.: Herder, 1964), p. 10).

Van Noort, Castelot, and Murphy specify that the canonisations in question are the final and definitive decrees by which the supreme pontiff declares that someone has been admitted to heaven and is to be venerated by everyone. The decree of authority that they attribute to the claim that such canonisations are infallible is 'sententia communis', the common opinion of theologians (van Noort, Castelot and Murphy, p. 117). Their evaluation of the authority of this claim is the more significant because they themselves agree with the assertion that such canonisations are infallible. There can thus be no intention on their part of minimising the authority of a claim with which they disagree. The assertion that canonisations are infallible thus belongs to the field of free opinions. It is not one that Catholics have an obligation to accept.

St. Thomas Aquinas disagrees, as do nearly all pre-Vatican II Catholic theologians.  "Exactly!" my rear end.  What a bad-willed fool you are.

Ok, i'll admit that it's possible, but until the Church DEFINES that the Holy Ghost also proceedds from the Son, it's just speculation.

If you want to argue that the pope could be infallbile outside of the V1 requirements, then 1) you'd have to read the V1 fathers and make sure that their intent was not to restrict such a definition to only that one area, and 2) your argument would be theological speculation, which does not require unconditional assent, so your assertion is questionable until the Church defines it.  In the end, you can argue that canonizations are infallible to the same degree as an ex cathedra statement but it's just your opinion.

Ok, then conditional assent applies to both, though the pre-V2 process has much more reliability due to its process.

No, I don't believe that there are ADDITIONAL ways for the the pope to be infallible, outside of V1's definition.  You say there could be.  I say, this is speculation since it hasn't been defined.  Your example of the 'son proceeding from the Holy Ghost' is a poor argument for your extra-infallibility proposition.