I love waht you say abou GRRM building his twists, I think that's true most of the time, but could you give some examples of unexpected twists? Am i wrong or Aegon's plot was only foreshadowed by the "mummers dargon" prophecy?
Unforeshadowed twists…well, let’s look at the show, since that’s a nice easy comparison to make.
The Red Wedding was extensively foreshadowed in the books. Dany and Theon both see the Red Wedding in ACoK, Dany in the House of the Undying, Theon in Theon V, as he dreams of Robb and Grey Wind joining a feast of the dead in Winterfell. Arya receives a more cryptic prophecy from the Ghost of High Heart in Arya VIII, ASoS. On top of the metaphysical, we see the political setup well in advance - orders for the disposal of the Lord Paramountcy of the Riverlands that Sansa knows can’t be effected while Robb, Hoster, and Edmure are alive/free, orders made for Stark men to march into a trap at Duskendale, letters sent to and from Tywin, Roose Bolton’s marriage to Walda Frey. There’s also the literary gag of the Freys controlling a double crossing. Just before the actual event, we see the “nice Freys” are absent from the Twins and the bride is shaking and distraught throughout. So when the killing starts, all the visions, all the oddities, they come together in a stroke.
In the show we see Robb do something that upset the Freys. He makes an apology and offers Edmure’s hand in marriage as compensation. He is led to believe, and through him the viewers, that the Freys have (ungraciously) accepted that apology. Surprise! The Freys get all crossbow-happy at the wedding reception. The meticulous foreshadowing and logistical set-up of the books can only be found in a few shots of Tywin writing letters. The only thing that suggests that the Red Wedding was going to happen in the show is that the Freys were established to be jerks and Robb pissed them off. The atmosphere of the show is consistent with the possibility of betrayal and murder; it does not establish that this betrayal and murder was in the works.
Aegon’s plot has been metaphysically foreshadowed by the mummer’s dragon prophecy, yes. But politically, we’ve also known that Varys and Illyrio have big plans from very early on. Varys’ speech about the perfect monarch is one of those moments that in a short amount of time makes sense of a lot of oddities - every time any character has asked themselves, “What’s Varys’ game here?”, here is the answer. The reveal of Aegon “VI” is the logical extension of the issues raised with Varys’ actions throughout the first four books, as the Red Wedding is the logical culmination of the strange political machinations towards the end of ACoK and the start of ASoS, as the reveal of Littlefinger’s manipulation of Lysa explains Jon Arryn’s murder, Sweetrobin’s fosterage, and the Vale’s lack of action in the War of Five Kings.
There’s still another shoe to drop, of course, labelled “Blackfyre.” We’ve got plenty of “the male line of House Blackfyre is extinct” and children’s clothing packed away in Illyrio’s manse to help foreshadow that.