The devil as always is in the details.
In Category C, the following points are added:
"5.
Alarm and signal weapons, salute and acoustic weapons as well as
replicas
That tiny parts at the very end is what would essentially screw airsoft as we know it. Under EU law a Cat C firearm is
Category C - Firearms subject to declaration
1. Repeating long firearms other than those listed in category B, point 6.
2. Long firearms with single-shot rifled barrels.
3. Semi-automatic long firearms other than those in category B, points 4 to 7.
4. Single-shot short firearms with rimfire percussion whose overall length is not less than 28 cm.
You are then almost certainly into serial numbers, shotgun certificate style registration and all the other limitations that buying/selling/owning real firearms places on people