> One of the main ones is that national policies around employee equity vary throughout Europe and are often severely disadvantageous (particularly Spain and Germany). Lots of European entrepreneurs are calling on policy makers to both normalize this within the EU, as well as making the policies competitive (e.g., [1]).

I would also add that employee perception about the value of equity vs salary varies across countries in Europe. High stable salaries could be preferred over equity in good welfare states with employee-favorable legislation where firing people is harder (Germany & France for example).