It is OK to purchase an asset for a game that you own / have interest in, and share that with other developers on the same team.
The way to do that, is that you download, on your machine, and "add to project.’
Then, you check in these added assets into the project, and push to your source control system.
Then, the other collaborators on the project will see the checked-in assets and be able to work with them.
The Epic Store / Marketplace integration only happens in the Unreal Launcher, and once you “Add to Project,” that’s a straight-up file copy. Once the files are in your project, there is no additional technical epic store integration, only the legal requirement to still adhere to the license of the assets.