Bartolomeo said they'd join as subordinate crews underneath the flag ship strawhat crews, basically like WB's subordinate crews that were working for him but weren't part of the crew itself
It's interpretable in different ways, to me I can't see it being anything other then them being a part of the SH's, the other current translation supports this
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. He says make us a part of your crew
as well, you're our boss and we're your followers. Notice he says "as well", meaning others have already done so, meaning the only option would be them being actually a part of the SH's since there are no other separate 'allies' that they would know about.
The ten man crew thing is a misunderstanding that most people don't bother to correct. Luffy said he wanted 10 crew mates before going to the grandline, he didn't say 10 members period and he ended up going to Grandline with less anyway. That was just a plan by Luffy a plan stated within the manga isn't the same thing as Oda planning something. Luffy will have more than 10 crew mates most likely.
Makes sense. If WB had 1200 (?) people in his crew and they were all mad overpowered, but he still couldn't beat the other Yonko and take their land, I'm guessing Luffy needs at least a crew in the 1000's. 100 people just get laughed at by every Yonko crew.