I’d like to recommend a decomposition of the Upgrade tree and changing it around with the Campaign concept.
What could this look like? We can use any campaign as an exemplar, but ultimately it wouldn’t matter where you start the key point would be that you wouldn’t have to grind some things too many times:
So firstly lets make a tech tree for soldiers and weapons - separate from Campaign, we’ll come back to it later.
Soldier/Weapon/Equipment/Vehicle Tree
So the soldier tech tree has Rifleman with appropriate classes I, II, III, unlocking Rifleman I gives you access to Assault I, and then Engineer I, Fighter Pilot I, Radio Operator I etc… You can scroll the Moscow Axis campaign to see the order of unlocks, I’m not worried about whether the order is right at this point, its just a concept.
For each soldier type we cut out the red rank tree out of the campaign and glue it into this core soldier tree. It is upgraded with XP exactly in the same way.
So in the end you end up with a Soldier type and their associated rank available in any other campaign after your initial grind, that includes perks etc…
Along the side of the soldiers are the weapon/vehicle unlocks and more importantly respective upgrades. Same thing, you start off with a weapon suitable for riflemen, or the base vehicles, an XP unlock all the subsequent options in some semblance of progression.
You can spend your “points” earnt in battles as you see fit - so focus rifles > SMG, or tanks > planes etc… however, the ability to equip the weapons remains extant.
In the end you will have an unlocked and upgraded set of weapons available for any campaign.
Gear equipment is a bit more random right now and not entirely rational, but it could similarly be cobbled into an independent tree with some semblance of thought that orders the available equipment a bit more logically than currently available.
New Campaign Progression
Now for the campaign itself, the progression goes with what can you bring to the game.
So in most base campaigns we automatically get the Rifleman squad, and Sniper squad from memory, but remember we still have the “blue” part of the upgrade tree, which is a bit of a balancer in its own right so you have to unlock this part for each campaign, yeah your soldiers are leveled up and have good gear but you still need to open up the squad as normal. The weapon/equipment levels now just become access barriers rather than having to re-grind the weapons from that point.
Now in terms of equipping your soldier/weapon we go to the current Stalingrad “cost” system, with a slight change, in that you have a range of costed soldiers/weapons/equipment/vehicles from basic to fully upgraded. Correspondingly you have to spend bronze and silver orders to buy the level of the weapon that you have available via unlocks for different costs - what those are will need to be playtested. You can chose to spend less orders to get a lower quality soldier/weapon and “trade” them in later much like the current system of selling weapons.
So each campaign still allows you to access different classes of soldier as per current squad concept, you still need to “build” out each squad, but once that its done you can go back to the “soldier/tech” tree and buy the appropriate soldier in accordance with accumulated orders.
You can throw gold at the soldiers and weapons, or even the Campaign progression to unlock squads as per current Campaign progression, however, what you can’t do is throw gold at upgrading the squad slots within the campaign, populating them - ie you have to buy the appropriate soldier for a given cost, or equip them with a quality of weapon for which you have sufficient orders.
This system will also allow for an overhaul of the squads themselves, which can be adjusted a bit more historically and potentially adjusted for all sorts of things from size to new abilities depending on the squad type and the respective campaigns. It can also be used to regulate the number and type of weapon more sensibly from both a historical and game balance view - ie no more full FG42 squads - you might get 1 - 2 per FJ squad only…