There's some (fairly simple) devices in use or that you can make yourself to turn bottles into a kind of thread, but it's very hard to automate because bottles will be different in shape and condition.

But as you say, turning them into something else isn't the critical part, collecting them in the first place is. The most important thing is taking them out of the environment so they stop breaking down into microplastics and the like.

Personally I think all these creative solutions for reusing plastics aren't so important. Collect it and put it in a giant landfill like an old open mine, bury it and forget about it until a future generation invents an efficient way to recycle it, then mine it like a resource.