Thank you for the feedback. I think I will remove the voting system for now while I figure out of solution. I will probably not be adding the user reputation system, unless I figure out a way to do it without facing the problems you have mentioned. As for collaboration, I will add a feature allowing app maintainers to set whether or not non-maintainers can add scripts without maintainer permission. Thank you again for the feedback, it was very useful!
The point is not to have the script directly install the program (e.g. getting the binary, putting it where it needs to be, and making a desktop file), but to have the script be used as a wrapper for any of the methods you mentioned above. This would allow for a more consistent installing experience, and in the future, a unified CLI. It would also be better for the reasons mentioned in my post.