There's always an "everyone blocks me and no one likes me" fear in hosting your own instance, and yes you will run the risk of preemptive blocks if people don't like how your instance looks.

The particular combo here, though, is "lurker only instance" that also spams follow requests. If you don't spam follow requests and are selective about who you follow (like a human rather than a bot), you have less risk of this specific paranoia. Lurkers are fine to many Mastodon users. Lurkers spamming following requests are a concern.