A bit more information Ive researched about some of the venues.
About Leeuwarden, I believe that they have one the biggest e
bition spaces in the country and have 7 halls.
• Friezenhal (Frisian Hall) 1, 2 and 3 approx. 13,750 sqm in total
• Saksenhal (Saxon Hall) – 8,925 sqm (105 x 85)
• Keltenhal (Celt Hall) – 4,080 sqm (85 x 48)
• Frankenhal (Frank Hall) – 5,700 sqm (60 x 95)
• Batavierenbalkon (Batavians Balcony) – 2,000 sqm
• WTC Passage – 3,500 sqm
• Entresol (Mezzanine) – 1,000 sqm
It is perfectly possible to covert the Frisian Hall into an arena of 10,000 people or more. Other halls could be used for the press centre as well as the green room.
I think the venue in Maastrict is undergoing a major renovation so it may not be possible to host it there.