You can't use a worktree without write access to the shared object database. You can use worktrees, or you can containerize your agents, but you can't do both.
I think you mean hardlinks the object database? The index (staging area) changes constantly. Not much point in hardlinking it.
Hardlinking the object database is the default behavior with you clone locally on linux. It's great for one-off clones such as CI/CD pipelines and agentic containers, but the benefit in terms of disk space saved is short-lived: as repos evolve independently, they replace their packfiles with new ones, and the new ones will not be hardlinked because they don't contain the same objects.
I like to keep bare repositories in dropbox, but I use `--no-hardlinks` when cloning, because before I did that, on one occasion, dropbox corrupted the bare repo, and my working repo was corrupted as a result.