Re: Luminous mysteries - Blessed Mother gave us 15 decades. An extension of that does not seem within the realm of prudence. I suppose you could say Hail Mary's and meditate on any holy topic... but Our Lady "invented" the rosary, and so it seems good sense to me not to tamper with it. If the Holy Father feels that those meditations are helpful to his soul, however, so long as there is nothing against Catholic teaching in them, I don't see why he can't pray them if he wants. Still he has never said: "henceforth all Catholics MUST pray the Luminous Mysteries." If tomorrow he recommends a meditation upon the obedience of Moses, I will receive it as an equally innocent suggestion. Nevertheless, the pope suggested those mysteries. He never expressly commanded all Catholics to pray them. (eg, under pain of sin, and not as a mere remark, "pray the luminous mysteries." One might as easily say "eat beef". If he meant to command it, he would have had to do so, methinks, quite officially, so that none of the sheep missed it.)
One can use one's own words or thoughts to pray for that matter, without sinning. Though in the case of the luminous mysteries, I think there is a subtle attempt on the devil's part to get people to focus disproportionately upon Jesus as MAN... On the face of it there's nothing wrong with someone getting spiritually inspired by the idea of Our Lord preaching, for instance... but when we focus too much on Our Lord as man, the danger is to NOT think so much about Him as God.
I also wouldn't recommend ecuмenical meetings. But the Holy Father remains the pope, even for that.
Perhaps you meant to recommend them yourself, however? (The Luminous Mysteries.)