@RyanHyde the middle ground already exists, and it's the current side-loading process, which requires you to *explicitly* choose a somewhat obscure setting, to allow installation of apps of "unknown sources"
someone who is sideloading will generally already know what they're doing, since they have to flip this permission on. even if done permanently, it's not a global option but a per-app option to allow such installs from, say, the file manager. malware detection via Google Play Protect is *also* already a thing, mentioned in the linked article
you appear to have assumed that arguing against centralized signature verifiers to be *allowed to develop for Android,* means arguing against *any* attempt at verification. instead, it's really just: "Android, let's not do exactly what Apple is doing to wall in the garden, thanks"
seems like the best middle ground would be for Google to simply, not do this thing