To me the more interesting question is rather which traits, styles, lore and visuals people want to keep from these factions if GW revisited them? What´s the things that actually draws you to a faction in question? For visuals it might be the bone constructs of the Tomb Kings that stands out and would be fantastic to see in a new way. From Brettonians the playstyle with heavy cavalry and cheap fodder troops could be fun to see re-used. Seeing a "death" faction break the mold and be rebels within the death Grand Alliance could be interesting. Just saying you want faction X back doesn´t actually say that much beside that you liked that faction as it was before getting turned to dust. Not to mention I doubt GW would just copy paste such a faction. Better then to highlight what aspect you want from that faction and keep sending that information to them. This might just be me that´s an optimist but it feels more likely that GW would re-use aspects of old factions, if they get bombarded with it rather then just telling them you want faction X back to play with.