@Saloma:
I could see why people would think Paulie would join… At first. For one, he had a very unique design and fighting stlye. Two, he was Sanji's polar opposite and a gambler. But then, once Franky was shown, I have no idea how people could think Paulie would join over him. ESPECIALLY at Enies Lobby. Did people seriously think Franky would say "Well, I just helped you save Robin, bye!"?
Exactly how I felt about the new crew member thing. At first I was pretty sure it was going to be Paulie and didn't even consider Franky. Paulie had the gambling thing, and he had that moment in the mansion where he seemed to connect with Luffy, so I thought for sure he would join. But then they actually started to flesh out who Franky was and show us his history, how he fights, his strengths and weaknesses, and how he has a connection with both Usopp and Robin. Pretty much after Franky had his flashback I think it should've become obvious he would be the person to join. And besides it just being obvious that Franky would be the one to join, he seemed to be the most appropriate. He has fantastic skills as a shipwright, a dream that fits in with the goals of the Strawhats, good fighting sills, and a personality that fits with the rest of the crew really well.
I guess if it wasn't going to be Franky, it could've been Paulie, but he became a background character so fast it would just feel wrong.