Implementing these sort of backup options should not result in a meaningful reduction in security as they don't effectively change the security model, encrypted client side backups are equivalent to the existing signal specific encrypted backups on android, device to device transfers are the equivalent of coping the existing signal specific encrypted backups to a new phone and restoring them. The desktop client receives copies of signal messages normally as well so it effectively keeps backups already(they just often end up incomplete and can't be restored properly).