I see where you’re coming from: you’re equating the purchase of a licence to play the game with the full extent of the code and resources actually installed on your game platform to play that game. But these things cease to be the same when you have paid cosmetic extras in a co-op game with what is effectively an in-game store (the New-U station, where you can see the premium heads and skins from the packs).
Let me put it this way: suppose you are responsible for developing such a game. It’s first-person only, so the main player benefit of having cosmetic extras (premium heads and skins which are more than simply a palette swap on the same model) is that they are seen by other players in the game. What do you do? Do you:
a) not include those resources, but force a download of them for every co-op partner who doesn’t have them whenever their partner joins their game
b) not include them and have the character ‘wearing’ the premium head/skin show up in their default outfit for the co-op partners (defeats the point somewhat)
c) include the resources in the download so they can be displayed in the co-op partners game, but leave them locked for individual use behind a DRM licence
In BL2 and TPS, Gearbox chose to use option c. They did something similar with the headhunter packs: for ease of distribution, they bundled some of them together as a single download, but sold them as separate licences. This bent a few people out of shape, because they felt the same way you did: they’d paid, downloaded code, but could only use half that code. But it wasn’t the code they bought; it was a licence to use part of the code.
And if you think about using option b, this means that if you want to see what a premium head/skin pack looks like, you’d either have to go to a web site or wait for the resources to temporarily download to your system whenever you tried to view then in the New-U.
In a way, it’s no different to buying any software package on physical media: you get the means to use the software, and a licence to use it. The system used in BL2, TPS, Battleborn, and many other games is simply an extension of this concept.
I understand if you don’t like that model of distribution, but practically speaking what other options are there? The only alternatives I can see are to include everything and then either raise the base price (painful) or sell the game as a subscription. (Or go with the full F2P model, with everything that entails.)
As things stand, I’m personally quite happy with the current model - stuff works, if I co-op with someone who uses premium cosmetics we both get to see them, and I can pay for as much or as little of such things as I like.