Given that Smartspacer already possesses Shizuku access, the plugins can be installed automatically in the background without requiring manual permission to install each time.
Shizuku access is only available with enhanced mode enabled, which would mean maintaining two separate paths for this feature
Showing the package installer is a layer of transparency when installing plugins from the repository, which theoretically may be malicious. The repository has a report system for this, but it's all manual - if someone were to compromise wherever the APK is hosted and replace it, showing the package manager would still show the name & icon of the plugin being installed, which makes it impossible to replace the plugin with an app with a different name.
Suggestion
Given that Smartspacer already possesses Shizuku access, the plugins can be installed automatically in the background without requiring manual permission to install each time.