Sounds a great idea.
Dan did a sound job on BABW, so +1 for his support.
I’d only combine with another event if there are benefits. If the union doesn’t provide any (or indeed throws up barriers or challenges) then it’s not a good thing - worth checking with organisers of such things and getting their view, but don’t hamstring yourself!
Venue should be appropriate, but also bear in mind for international travel, both accessibility of an airport and also decent, inexpensive accommodation is a strong draw for people willing to travel.
It can be worth making a weekend of it and having a more casual ICE Breaker, draft or other activity (or several) the day / night before the main event.
I can offer advice and support, but I don’t want to actually do anything! I do that kind of thing in many other arenas of my life and Netrunner is the thing I get to just turn up and play at.
London, Brussels and Amsterdam all sound viable, just be aware of getting a decently priced location may mean being inconveniently placed for other facilities. On the other hand, if you pick somewhere near one of the cheap airlines that problem might solve itself (e.g. Brussels Charleroi is far outside Brussels itself, but that might make it cheaper for accommodation and venue, while still being relatively convenient to fly to).
I’m aware more continental Europeans can just drive somewhere, so my views may be slightly tainted by being based in the UK!
FFG aren’t going to have a 2nd Worlds in Europe or anything, but they might be interested in prize support if you contact the organised play. Similarly, once a location is decided upon it’s worth contacting the distributor for the region to talk about prize support. Crowd-sourcing among the community for prizes is also viable (Chaos Theory or Ken Tenma anyone?).
I definitely think there’s scope for a European Tournament and getting some branding or more more professional looking trade dress round it and making it an annual thing.
The tricky bit might be getting the right date!
Good luck. Happy to throw things in from the peanut gallery as and when.