we’ve been exhaustively experimenting with github organization roles/permissions settings, to enable our developer community to collaborate, but can’t find a solution.

• our repo has a large git lfs data library. for this reason, it’s not feasible to expect devs to fork our repo, because it will soon exceed their free github account lfs data quotas. this means, we need to be able to add them onto an organization team, that allows them to push branches.
• we can’t figure out how to enable the members on that team to push branches without being able to overwrite or delete other user’s branches.
• we want users to, effectively, have ownership over their own branches, without being able to disturb branches created by other users on the team.
• as an open source project, we need to allow hundreds of collaborators onto this team, and we can’t vet them all to ensure they have good intentions. we need to allow them to contribute without doing damage to the work of the other devs.

what settings might we be missing or misunderstanding? is there a valid way to configure this project to securely enable open source collaborations?