..What they will mostly do is instead of making a whole transaction worth 10,000 they will just do two 5,000€ transactions in order to remain undetected. ...
Regulators are well aware of this phenomenon.
The practice of splitting up transactions into smaller transactions in order to bypass
reporting is called Structuring / Smurfing.
https://en.wikipedia.org/wiki/StructuringYou will not go undetected if you try this, because banks are also obliged
to report Structuring / Smurfing in most countries in the world.
E.g. they might not report you for making a transaction above the threshold, but they
will report you for suspicious activity, which is even worse for you as a customer
than the standard reporting.
That's right. Even before this 4th AML directive, existing ones already do very well at detecting these.
Not only that - these structures and smurfing are now very easily thrown up by simple, relatively cheap software. A lot of tweaking is done by people to do this - not just splitting up of transactions, but regularly going just under the various limits. These patterns themselves are also red flags (or at least, orange flags). And like you said, in many cases, it is actually far better to properly report going above the thresholds than it is to go below.
The timing of this directive is also coinciding with the enforcement start of GDPR too, so it will be really interesting to see how this plays out with Bitcoin-related enterprises.