They are opening cinema's, shops, pubs and restaurants all of which are inside. Then surely there is scope for arguments sake letting 1500 people into a ground that holds 10,000. Most grounds have 4 stands/open terraces that can be used to spread out people and one way systems will be put into place. The biggest issue would be everyone leaving at the full time which would need a bit of planning. At the end of the day you are stood/sat outdoors.