Brussels in 2001 would be fun, at the very end of Sabena’s tenure as Belgium’s national airline. Layout is nearly the same though the circular terminal near the bottom is in full use and the cargo ramp isn’t as big.
It could really make for an excellent more historic airport that you could operate as a current one or as one from 2001 providing players, like me 
, with more choice as you could have Sabena, Sobelair and Virgin Express at the airport, plus if you wanted a later 2000s style you could have SN Brussels Airlines. It could really fill that hole between LHR and the rest of Europe and wouldn’t be such a massive drain like AMS (Though ofc I’d love to see that too).