No to mention the giant-robots and other cool stuff we might see if they explore the fact that Vostroya is basically half a forge world. So a good opportunity to see some extra tech priest models and, Dare we hope, Skitarii/Tech-Guard models.
also while we’re at it, rules for carapace amoured mobs of infantry (no vet spams needed for a stormtrooper rush type list). Something to reflect their reputation as urban combat experts like close order drill (old doctrines system/rules themselves resurrected like the space marine’s chapter traits?), or move through cover and maybe stealth (ruins)?
Considering Vostroya has the stigma of having defied the Imperium during the Horus Heres, split loyalty/responsibilities between the ruling Martian and Imperial interests, they would certainly have the fluff pages filled out fast.
Similar arguments could be made for the other guard books too. If they wanted to release an immutable set of Regimental traits for each one they could just tie it all together in a “Regiments of the Imperium” book(s).
White Scars! They are more divergent than than Blood Angels were before ward. They had brotherhoods spears tulwars And possibility to expand with new fast predators with no side sponsons. Not to mention the fluff about them having familes from way back and their primarch riding on top of his rhino pulled by mechanical horses. Crazy stuff. Better than the Sanguinor…
I threw my vote in for Cadia (mostly because Eisenhorn made me love their fluff, and Kasrkin have a lot of potential), but I’d love to see a Space Wolves 13th company supplement. I don’t even play them, but it has a lot of flavour.
If it’s restricted to 6th edition codexes, then a tzeentch or khornate daemons supplement. If its pure wish listing then a grey knight supplement for the exorcists.
Jaded Gamercast 
Vostroyans, if only for the hope that they release them in plastic
No to mention the giant-robots and other cool stuff we might see if they explore the fact that Vostroya is basically half a forge world. So a good opportunity to see some extra tech priest models and, Dare we hope, Skitarii/Tech-Guard models.
also while we’re at it, rules for carapace amoured mobs of infantry (no vet spams needed for a stormtrooper rush type list). Something to reflect their reputation as urban combat experts like close order drill (old doctrines system/rules themselves resurrected like the space marine’s chapter traits?), or move through cover and maybe stealth (ruins)?
Considering Vostroya has the stigma of having defied the Imperium during the Horus Heres, split loyalty/responsibilities between the ruling Martian and Imperial interests, they would certainly have the fluff pages filled out fast.
Similar arguments could be made for the other guard books too. If they wanted to release an immutable set of Regimental traits for each one they could just tie it all together in a “Regiments of the Imperium” book(s).
White Scars! They are more divergent than than Blood Angels were before ward. They had brotherhoods spears tulwars And possibility to expand with new fast predators with no side sponsons. Not to mention the fluff about them having familes from way back and their primarch riding on top of his rhino pulled by mechanical horses. Crazy stuff. Better than the Sanguinor…
Valley of the Carnosaur
Steel Legion
I threw my vote in for Cadia (mostly because Eisenhorn made me love their fluff, and Kasrkin have a lot of potential), but I’d love to see a Space Wolves 13th company supplement. I don’t even play them, but it has a lot of flavour.
I think 13th company will be a core part of the Space Wolves codex when it gets redone. I couldn’t see it becoming it’s own supplement.
Raven Guard!!!
If it’s restricted to 6th edition codexes, then a tzeentch or khornate daemons supplement. If its pure wish listing then a grey knight supplement for the exorcists.