Worthwhile reading
Though there is a mention of 8.) Simplification of Belgian airspace, I did not find any details...
Their controlled airspace isn't hard. What can be extremely difficult to interpret are the multiple layers of restricted and danger airspace.
They need to be simplified immensely, as clearances through one or some but not the others will be a living nightmare.
To cross Belgium it helps to go a bit north of that area.
France is like that too, east of Paris...
However the military will not give up their protected bits easily.
Not saying they should give it up, but why not simplify it into 3-4 spaces, like EG D 036,037,038. They don't overlap.