Just going to jump in. All of us can probably agree that the SHs are comparable to the Roger pirates. Most of us also assume that the SHs will face the BB pirates in a one-on-one battle.
-If we take the above as true then the SHs lack one crew member, besides Jinbei who hasn't joined jet, to face BB.
-And they are also missing two kids/cabin boys/apprentices like the Roger pirates.
I think both situations can now be resolved. First off, there is only one SH missing if you count stronger as a member of BB's crew. I say let us count stronger as an fighting appendage. That would mean that one of the SHs would then have one too, the missing pet as some has suggested. I think the semi-member, the fighting appendage, is General Franky. It fits even if it is not a creature, it is an extension of Franky as Stronger is an extension of Doc. Q.
Secondly, Roger's crew as far as we know had three 'temporary' (for lack of a better word) members: Crocus, Buggy and Shanks. Though we don't know how long or when the last two joined, I think it is safe to assume they didn't stay until the final island. Why else would Shanks want to return to Raftel? Crocus I think is embodied in Jinbei, as he will be joining only for the final stretch of the journey. This leaves us with the missing equivalents of Buggy and Shanks. If indeed Shanks and Buggy were only a part of Roger's crew for a short period, then Kinemon and Mononosuke will fit in nicely. (Yes, Kinemon is an adult, but Chopper is not. Oda mixes things around as much as he likes his patterns.)
So no new crewmate execept for the temps.