If you want to dive into Flames, Heavy Metal and Storm Division (Which I think makes sense, storm divison will get an update towards the end of the year also btw)
Your list looks very well researched actually. If money is not the issue you can pretty much go ahead and have a good collection. But a few things might get costly fast, while you do not really need them (driectly) I think.
Then these are my thougts:
Stryker 1
Stryker 2 Both definetely!
Stryker 3 Could work, but maybe don't give priority
Haley 2 Not so expensive, can't hurt - do buy Thorn as well if you want to get her!
Haley 3 Only if you are ready to dive into the depths of her kit, which might take a while, maybe get later or wait for a good deal?
Blaize 1 Yes
Blockader
Gallant
Nomad Not sure about the Nomad, you can only take him in Flames! And there you usually have Toros, Gallant and maybe one "normal Merc Jack" or just one Blockader. These other 2 are kind of set - but they will only work in Flames
Ironclad
Thorn
Squire
Mangler Not 100% Sure you need so many merc Jacks, I think Toros should be priority
Stormclad
Toro
Charger
[Firefly] Very importants in Storm division, is also included in the starter set!
Alexia Ciannor & the risen
Eilish Garrity the occultist
Alexia the undying
Grand master Gabriel Throne
Artificer prime nemo
Captain Arlan
Major Katherine Laddermore Laddermore only in Storm Division, but since you are getting some of that - yes!
Savio Montera acosta
Alexia mistress of the witchfire
Ragman
Journeyan warcaster
Stormsmith Stormcaller
Stormblade captain All looking good so far!
Thamarite advocate
Legion of lost souls
Morrowan Battle priest x2 You want more. Really. I'd say at least 4. You want to hang 3 at a unit of Precursor Knights and then at least a sinlge one at another random unit!
Order of illumination Resolutes x2
Precursors knights x2
Precursor knight officer x2 With those 3 things: I would not get 2 of them instantly. Better one each, then also a unit of villigants and legion of lost souls. If you want doulbles of all those things, you need a clear plan of why you bringing them and the second unit will see a lot of time on the shelf. So I would start with sinlges and then see.
Storm lances (x2) Two Storm Lances are not optimal right now - but it can't really hurt to have two if you do not want stom blades.
What I am missing is Maddox, she should be good in Flames and also in Sotrm division. If you can get half a 2 player battle box for cheap I would get that. Yes 10 Stormguard are useless (unless they finally make them better in the storm divison update?!) but htey are basically free if you want that sinlge ironclad (to make it into galant) anyway, as well as the firefly.
Another thing that is not on your lists, but never bad is a Storm Strider (HM and Storm Divison) and maybe nemo4. ALso Cygnar Collossals are very good. All three of them are big and expensive, so if you want to focus on Flame mostly (which is good), then the blockader is good.
If you save a unit of precursors with UA and Resolutes, the Nomad and Mangler, as well as Haley 3 and Stryker 3 for later - you can get the thing you really NEED right now:
Morrown Archons, two of them. I do not know if the stryker Archon is still in the PP webstore, that is a cool variant model. You can also think about Thamrite Archon, but the Morrowan is key to Flames. Thamrite are also good, but less "auto include".
here is abit of material on Flames as well:
www.loswarmachine.com/theory-and-tactics/2019/12/15/cygnar-flame-in-the-darkness-initial-thoughtswww.loswarmachine.com/theory-and-tactics/2020/2/24/order-of-illumination-vigilants-the-most-deceptive-of-modelswww.loswarmachine.com/theory-and-tactics/2020/1/6/some-thoughts-on-the-thamarite-archon-warmachine-and-hordes-tacticawww.loswarmachine.com/theory-and-tactics/2020/1/17/morrowan-battle-priests-make-the-theme-go-roundwww.loswarmachine.com/theory-and-tactics/2020/2/24/some-thoughts-on-order-of-illumination-resoluteswww.loswarmachine.com/theory-and-tactics/2020/2/2/legion-of-lost-souls-the-coolest-skeletons-on-the-blockWow, thanks a lot for your time and your thorough explanations ! I will dig deeper then !