For the record I don't think anyone is complaining tha Tymanther still exists along side Unther, its just that alot more of the 4e changes appeared to have remained them expected, but most of the good stuff came back, so I don't think anyone will have a problem with the 4e remanants.
The 4e remanemants that I found are Tymanther, a floating Airspur, the Elf Harrows, Dragonborn, Dambrath as being a werenation inside of being a half drow nation, some of the geopolitical factors, Many Arrows sort of, the Feywild, and odds and ends.
As for what I'd like to see in a FRCG.
This is just a possible example:
A chapter on the planes, and the Gods including all the Gods/demigods/archdevils/primordials from 1e/2e/3e/4e and any new additions from 5e (and there is new additions, there is a new Gnome God and Ra and Horus split again as are Lanthander/Amauthor). This includes the Mulhorand, Unther, Monster (Gobliniod, Giant, Dragon, ect...), and the Imperial Buracary of the Shue, enough Shue have immigrated to Faerun in Westgate, Thesk, Tezziir, Nethlekh ect... to justify this.
A chapter on the sword coast, including its islands.
A chapter on all the kingdoms of the Lands of Intrigue, including Amn, Tethyr, Calimshan, the Lake of Steam, ect...
A Chapter on the Old Empires including Mulhorand, Unther, Chessenta, and I'd include Tymanther, High Imaskar inexile and Mulhorand off shots like Thay, Moghom, and Sempar in that.
A Chapter on the Heartlands, Sembia, Dales, Cormyr, Eltur (misspell it), Westgate Nathlan, the Moon Sea.
A Chapter on the North, Vaasa, Sossil,Damara, ect..
A Chapter on the Shining South, Dambrath (amd the underdark beneath it), Ulgarth, Dupar, Estagund, Luirien, Var, Halruaa, any remaining beastlands.
A Chapter on East, Alagorond, Rasheman, Narfell, ect...
A Chapter on any other regions.
A Chapter on other Continents of Toril, doesn't have to be detail as the other chapters, hell you can even keep returned Abier if you want as well as Maztica. This will give those who like less detailed areas somewhere to explore, while giving of us who wantca more detailed core Faerun what we want in the other chapters.
Not every detail needs to be given, but enough that can set a campaign anywhere in the realms. See 3e FRCG as an example.