Clearly you don't know what you're talking about. Chopper's dream was revealed during his flashback, in chapter 145, almost ten chapters before he joined the crew. Nami officially joined in chapter 95, after the Arlong Park arc, which is of course debatable. Still, her dream was revealed to us readers before that, in chapter 77.
Your argument about how a dream could be revealed close to the end of the arc, just like with Robin, Franky, and Brook, is, of course, correct. However, Franky and Brook's dreams were hinted at before the end of the arc. Franky said he wanted to make a dream ship in chapter 357, but left out the part where he'd like to be the shipwright on said ship. We already knew from the start that Brook wanted to meet Laboon again, after his talk with Franky and Robin. Robin
Brook needs to travel to meet Laboon, Nami wanted to draw a world map out from what she's sees in her travels, Zoro's dream doesn't require traveling, but it's close to impossible to become the best swordsman without going to the New World, and Usopp wants to become a brave warriors of the seas, which requires traveling. Chopper doesn't necessarily need to travel, but it's obvious that he wouldn't have been able to cure every decease out there if he stayed on Drum Island, or Sakura Island as it is called now. He doesn't, in theory, need to travel, though.
Luffy, Zoro, Nami, Usopp, Sanji, Chopper, and Franky - all the Strawhats, except for Robin and Brook, had their goals established within their own flashbacks. Robin and Brook said straight out what their dreams were - Robin in chapter 218, almost two hundred chapters before her past had been revealed, and Brook in chapter 459, thirty chapters before we got to see his past with Laboon. So, the dreams are either established in the flashbacks, or some time before. Never after, from what we've seen so far. Viola, Rebecca, Bartolomeo, and Kyros, all have had their pasts revealed, without any dreams established or even as much hinted at. Neither were their pasts anything to brag about, except for Kyros', in my opinion, very emotional flashback.
Bartolomeo's dream, if it's something along the lines of joining the Strawhat crew or travel around with them, would not lead to any development for him. It's not a good enough dream, if I can say that, to actually join the Strawhats. Again, I'd like for Sugar to join. It's not biased, it just makes sense to me.