Ok I have read a few of the concepts on a new crew member. Perhaps for the Logia type as it would be cool to follow someone who has just attained that DF on the sea, see how they learn to control it, learn new moves or heck what would give them ideas for moves as thats one of the things I enjoy about One Piece, they introduce like a common object then Luffy or someone will take that and invent a badass move with it.
As for the Ussop and upgrading to guns, sorry NeoKakarott I dont agree, I prefer Ussop not using guns and I dont know why but if he were to 'graduate' to guns as you said I would feel that he would become too similar to his dad in the Red Hair Pirates who we have all seen has been wielding a gun. Now its not that I dont think the guns cool or anything but what else can you do with a gun ? Ben Beckman uses it as a club yes, but would Ussop have the guts to do that ? I like it more the fact he creates new and interesting shots to use, some yes are for comic relief but then theres the badass one like the Firebolt Phionex thing he used to destroy the WG Flag back in Enies Lobby Arc.
Now onto the ideal crew member I would like to see, from all the characters weve seen in One Piece universe there is one type of character who I think would be funny to be in the SH Crew, now here is some links to some of the characters I am going by, sorry but I cant find the link to the Red Hair Pirate who is similar.
Now I think a Male character around Luffy Age. But the reason I chose Doma was because I think the concept of him fighting while his monkey on his back fights with him was so freaking awesome, loved his small segments during the anime adapation of the War on Marineford. So yeah I think a male crewmate with a monkey would be awesome to join up with the SH's. I mean Chopper obviously could communicate with the monkey. Comic relif effects could be the monkey always stealing Luffy hat or something like that. For those who watched the anime of the War on Marineford then you will remember some of the stuff Doma was able to do, and the monkey on his shoulder wielding a gun, just a imagine a younger version of him as the next member of the SH and thats who I am thinking.
: My bro is dead. He's gone! But he's there on my back, and here in my heart! He lives on as a part of me! If you're gonna dig, dig to the heavens! No matter what's in my way I won't stop!! Once I've dug through...it means that I've won! Just who the hell do you think I am? I'm Simon. I'm NOT my bro! I'M ME!! SIMON THE DIGGER!
: Your drill is the drill that will pierce the heavens!
(All quotes from one of my favourite Anime Tengen Toppa Gurren Lagann)