I understand your argument for Ace not joining, and I agree, but you realise you're just being an ass in this post, right?
I mean, I felt the same way about Margaret, and was still shot, stabbed, and burned for expressing my opinion. I didn't even express it as strongly as you have.
Marg had a great chance of joining before Luffy heard Boa's story. Now it's either Boa or a new character. It depends on how she acts in Impel Down.
So either her, or no one.
…Strange how in all these wacky speculations, no one's thought of one of the OTHER Strawhats bringing in a new nakama... it's not impossible, just there are no candidates yet, cause we haven't seen anyone specific (no names).
We all post differently. Whether or not I'm being an ass isn't all that relative to me since somebody else might see it another way.
It's possible for another SH to bring in a candidate for nakama but it's still kinda up to Luffy in the end. Besides that I think now we'll have to wait until the crew is back together before the next nakama thing becomes more clear and easier to discuss.
The longer Luffy is w/o his crew going to ID every new character Oda introduces will most likely be shouted as the new nakama by somebody.