Great post. Let's not forget how much Barca struggled in recent years. They sucked for a while, and it took them a while to build they have now. The same goes for Arsenal. But unlike Barca, Arsenal never fell out of the top 4. I think in some years time this team will be great, and hopefully Wenger will finally get the credit he deserves.
The thing with Samba though is I don't think you can bring in a CB mid-season, and I think that's what Wenger thought. Also, he may have tried to buy him and maybe Blackburn was being unreasonable about the price. They can't spend too much on a 5th CB, especially when they already have two imposing CB's in Djorou and Vermaelen who are better players. And Squi will be better next season too of course.
I'm not aware of Rossi's release clause, but that's a lot of money to spend on one player, especially if he'll be a back-up. Rossi wouldn't play on the wing I don't think he'd be a striker and would only be there when RVP is out. And knowing Arsenal's luck, if they went out and bought Rossi, RVP would have his first injury free season.
I do agree with you about Lavezzi, if they can get him for cheap they should, but I have a feeling he would be expensive. Also, he wouldn't play much as Arsenal have Nasri, Walcott, and Arshavin on the wings and we can't forget about the development of Vela and JET. He'd be a back-up for sure and he would stunt the development of some of the youngsters. I think getting Lavezzi would be a good idea but we don't know his price, and he may be too expensive for someone who wouldn't be in Arsenal's starting XI. If there is a long-term injury to Nasri, Walcott, RVP, or Arshavin next season and Arsenal is in the title race, they should buy him.