I've never been to a Smash-tourney in my life before, but I would still like to say some things, considering I will be visiting Brawl-tournaments and hope they will be enjoyable. I've written something about two of your points already, I'm still thinking about the other ones.
# Venues
I would try and get a big Venue where people can play and sleep. This way most people are already there and it's also good for the atmosphere, I think. Separate halls, because some people are weird and play till they fall asleep: others might not be able to sleep then and play worse the day afterwards. >.<
Hotels in Europe are a lot more expensive than hotels in America. Europe is more expensive for everything, but rooms really are expensive here. Anyway, Marc said that he rented a house/room with some friends, which I think is a good idea. Perhaps you should contact the hotels that are close to the event and ask them if they can do it for a lower price. A smart manager would do it, because it will give him more profit, because more people will stay at his hotel.
Perhaps a combination of both?
# Sponsorship
Sponsors are always fun, but you have to compare two things. What do they have to offer US and what do we have to do for them? If you get really interesting stuff and all you have to do is put their name somewhere on the poster/walls in the Venue, then it's no problem, I think. But if they want you to name their tournament after their company, they make you say their name every five minutes and so on, don't. Sponsors aren't really necesarry after all, because the bigger tournies have an entrance fee and that should cover most of the costs already. If not, all costs.
I was also wondering: who would sponsor these kind of events? A sponsor wants to have a "result" out of sponsoring something. In the case of the tourney being in for example Sweden, a local shop isn't going to sponsor because a lot of people will come from across the country or other countries. It's not like you're going to buy anything there just because they've sponsored a tournament you go to. Unless you get like 50 percent off, I don't know. Perhaps webshops? Need some thoughts on this...