I have been researching the GIRM, Code of Canon Law and other sources (articles & forums) for the answer to the same question (may the homily be given before the readings)!
I just wrote it on the CA Ask An Apologist forum, so will have to see if it shows up there. It sometimes takes a while.
I do not think it is ever permissible to change the order of the Mass, like giving the homily before the Gospel. This actually happened this weekend at our parish (and it has happened in the past with a different priest). As we are still recovering from a scandal where a pastoral assoc. was found to be a member of Call to Action, this was not easy to bear. I actually felt ill after that. And the homily was a “feel-good” fluffy one at that.
We are about on the verge of leaving for another nearby diocese/parish anyway. I hate to leave fellow parishioners, some of whom do not even know their liturgy is being abused, but this neighboring parish is really more immersed in Catholic practice and culture. I think my dh, a recent convert, would enjoy it & I think I would, too.