Trademark law is actually pretty useful. I say this as someone who is generally quite anti-IP. If you really want to not involve trademarks, just don't enforce it, and you'll lose any trademarks you've got afaik (IANAL, this is not legal advice etc).

What exactly is your worry here? Imagine you've started your project with distinct branding of Foo, and someone comes in and does something you really don't like. Maybe it's adding a gaping security hole in the name of adding a "feature". Maybe it's saying "this project is for Nazis only". The traditional response in open source is to say "fine, you do whatever you want, but create your own fork in a way that won't confuse people". IMO that's fair and square. What happens though when your project Foo gets a bunch of complaints because someone created a "foo" package that secretly replaces all of your keyboard input with swastikas? Trademark lets you say "don't name your package foo, because it's confusing to us non-Nazis".