That's not really feasible or realistic to expect that small shareholders would care about what kind of mini's GW makes or what army's rules they put out. 99% of those people invested in GW because it was either a solid stable stock or they don't even know they are invested because their 401K's put stock in there without them knowing.
However money does talk, and if GW sees their (limited) BT products being purchased heavily they might, might consider investing additional time and money into new sculpts. The problem with that is aside from the upgrade kit(which I'm personally flush with at the moment) there aren't really any models purchasing more than once.
Regarding Formations, they are dead and will almost certainly never appear in 8th.
And there, the Marshall schools the Initiates, hopefully deciding at least some are worthy of promotion to Swordbrother.
Still, if you want to influence GW
's handling of the Black Templars, then consider that after all the codices are released, we just may see campaign books. I agree that formations are dead, but there is the possibility of new Stratagems, and missions, maybe even relics.
In terms of products, the best thing you can do is get a concensus of what you would like, within reason, and remind GW
that if they make it, you will buy it. Think about it from their POV, how do they get Marshals and Chaplains, with sizeable forces already, to spend more money on their products? Also, what could they do to encourage new players to build a Black Templar army?
A Start Collecting box with the new Chaplain, an Assault Squad, and a Scout Squad? With or without the upgrade, or perhaps just a mini upgrade? Stuff like that, it's a starter Crusader Squad with an HQ, for an out of the box patrol detachment. GW
has learned that the smaller the out of the box to on the game table gap is, the more players will buy to add to their collections.
See, they already have @Firepower's money, and mine. So, in our cases, we are either tempted by another faction (Ad Mech in my case), or the Forge World products. GW
is less worried about prying more money out of us, and more hoping that we expose more gamers to the hobby, who will start investing in their own armies.
So, if there is a BT campaign book coming out, perhaps instead of your existing named characters featuring prominently, it should feature a newly anointed Marshall being sent off on his own Crusader. It is a great opportunity to explore fluff, but it is also a dressed up guide to collecting a Black Templars Crusader of your own. A brand new Marshall, assigned an experienced Chaplain to advise him. He chooses a Castellan from among the Swordbrethren that were once his own peers. He is even allowed to choose a very few to accompany him, at least one to be the Ancient to carry his heraldry into battle, as he builds his crusade. And, of course he will need an Apothecary. That just put the idea of buying a Command Squad box out there. The focus can be on his decision making regarding what to start off with, and what he will have to add as he goes. He will need a Techmarine, to maintain the Tanks and bikes, and (with the Apothecary) inter severely wounded brothers into Dreadnought sarcophagi.
See, that marries the opportunity for great writing with a collector's guide and/or escalation campaign. Quite possibly a product experienced players would enjoy, but also a product to lure someone else down the rabbit hole,and they will be shouting "ZEEEEEEEEAAALLLL!!!" the whole way. Mass appeal, and the opportunity for GW
to make money for their shareholders. Properly pitched, and developed, that could be a real golden goose.