Like would it be good if we could create a system that somehow will make the life of criminals who use Bitcoin harder?
That's not really a good idea.
If you create a system to make the life of <usergroup-A> harder, what's stopping you from using that same system to make the life of <usergroup-B/C/D..> harder for whatever reason you can think of.
Bitcoin is permissionless for a reason.
Yes! That's the problem. I don't see a solution to it and I think that is what will hunt Bitcoin for the next years.
We see that government doesn't want to adopt BTC and criminal use of it is one of the key arguments they have against adoption.
I think the problem of taxing Bitcoin might play a bigger role for them, but they probably will use the "dark web money" argument a lot, and our community has no answer to that cos that's how the technology works.