Baja, I think you're underestimating the sixers' very possible desire to just get the best prospect on the board, and that is clearly Evan Turner. Turner may not be the PG that they need, but he does give them the playmaker, shot creator, and leader that they need. Iggy really doesn't do that. While they could use a long term solution at C (and I don't discount the possibility of the scenario you describe) they need a perimeter leader more than anything, and Turner can fill that role. I see them trading Iggy or Young to accommodate for Turner before I see them either taking Cousins outright or trading down for him. I hope you're right though.
As far as Minny goes. I don't disagree that people are making good arguments for why Minny might not want to keep Cousins, but they're not making good arguments for why they wouldn't just take him and trade for that wing player that they need plus some extra goodies.
About your point on Pekovic and Milicic. While I think Minny is high on both these players (I remember liking Pekovic a lot when he was drafted), I don't think they let players that are likely rotational players at best dissuade them from taking Cousins, unless they thought the difference in trade value between him and Johnson (assuming the decision is between those two) was insignificant.
One reason they may want Cousins over Jefferson is that Cousins has better potential defensively at center. Size wise he matches up much better with the centers in the NBA, specifically Andrew Bynum. They had Kahn on NBA TV today and he was talking about how there isn't a problem between having Love and Jefferson on the floor at the same time, offensively, but there is a problem with them on the floor at the same time defensively, because of (namely) the Lakers and Gasol/Bynum. I think they eventually move Jefferson as opposed to Love, in the long run.
While I agree with you that there are still good big men prospects left, the big disappointment is that we were in a pretty good position to be guaranteed to get a prospect that had a very good chance at being a difference maker, but instead are left with good prospects that have decent shots at being solid players. So while I agree that there are good prospects left, better than maybe some other drafts, the disparity of apparent talent between Wall/Turner/Favors/Cousins and the rest is pretty big. If there is that difference maker available in the next tier of prospects, it will be much harder to predict.
Udoh? I like, but I'm not convinced of his upside as a go-to scorer, and I'm very concerned about his lack of defensive rebounding. That may be because of his system, but we don't know for sure.
Monroe? More of a Gasol light than Webber light IMO. IMO, he has the best chance at being a go-to post scorer than the others within this tier, but he gives us yet another post player that severely lacks defensively.
Orton? I like, but we may have to trade down to justify taking that kind of risk at the 5th pick.
Aldrich? A solid addition that would provide a big need, but he's not that 2-way difference maker that we were hoping for. Hence, the disappointment that you see.
Davis? Really hard to tell. My mid-level projection with him would be a Haslem type player, but who knows when it comes to him.
Johnson? I agree that his ball handling is probably going to limit him from being a high level shot creator, but people seem to forget the primary reason that made Danny Granger so undervalued in the 05 draft; it was his ball handling/shot creating ability. Not saying they'll necessarily end up being the same type of player, but even if they can't improve their ball handling to elite levels, if you have the shooting, length and athleticism, that margin of improvement they can make with their ball handling can end up making a pretty big difference. Besides, he's not that bad of a ball handler, he's certainly better than Aminu.
A big thing people keep missing about Johnson is that he's very active off the ball and has all the ability to be a very good off-ball scorer, which is so undervalued in the NBA, by the league, the media, and the fans. We can't capitalize on this ability as much as teams with true pass-first PG's, but I beg the people here to not just discount it. I'm not saying I'm a Johnson advocate per se, but lets not tear down his upside just because he plays a position that we're loaded at.
And finally, we need the best player possible, we need a core piece with this pick. It's hard to rely on the FA or trade market to nab those pieces, the draft is the best bet for a market like us IMO. If that best player is a big, great, that's awesome, but if it isn't then we're just going to have to take him and figure out the mess later. We can't risk losing out on overall talent because we're currently desperate for a big. We're (outside lottery luck) likely to keep falling lower in the draft over the next few years and our chances at difference makers are going to keep falling. So we have to approach this pick like we may not be in this area in the draft again, although it's still very possible we will. Whether we fill in our immediate holes now or not, we're never going to be a championship contender unless we have the star core players to build around first, and Evans alone isn't enough.