Alou is the prototype.
I think the key is having the ability to pick up where your cleanup man does not produce. By that, I mean you want the cleanup man to go ahead and use his power to drive in runs. But that can also produce high strikeout rates. Also you want the cleanup man to have that mentality throughout his AB. Jeff Bagwell never changed his approach to hitting when he had two strikes on him. Of course, Bagwell was not a cleanup man, but his approach with two strikes sure reminded me of a cleanup hitter's approach.
That is why your #5 guy is important as an RBI guy. He can have both power and high average as part of his staple. But with two strikes and ducks on the pond, he has to drive in those runs. He can't leave it to the #6 or #7 or even #8 guys to be run producers. Swing the bat is key, not take a walk. However that guy has to have the type of approach that can go with a pitch wherever it's thrown. He'll settle for singles and doubles if it drives in runs.
The oddity in the Houston lineup is that Carlos Lee is perhaps the closest thing to a true #5 hitter than anyone else. But Houston lacks a cleanup man so badly, it would be hard to move Lee off that position. His approach with two strikes is thing of beauty, but face it, when you have a slow footed bunch of guys on the bases, it takes more than just a single to right to score runs with this team. So Lee's ability to get that single when he has two strikes on him is somewhat wasted as a run producing AB. It becomes more of the "keep the line moving" AB and leaves it to the #5 and #6 to be run producers.
So what to do for next season (and perhaps for the rest of this season) with the lineup? I dunno, that's up to Garner and Purpura to figure out. If they're going to keep Berkman and Lee in the three and four spots, then you need good options for the leadoff and two hole. I love Loretta, but he's slow footed so you would need a great leadoff guy to compliment Loretta's ability. If you don't, then you need the one and two to be a little faster around the basepaths than what Houston has shown this year. Often times I've seen Lee double to left with Loretta on first and have Loretta sitting at third base and Lee at second with two outs instead of a speedster scoring from first on that double by Lee. The reason you have two outs of course is leadoff and the three hole have been inconsistent this year. I think the three hole will fix itself by next year (maybe even by end of year), but leadoff is what Houston needs to pay attention to this offseason.
All that brings us back to the #5 spot. Is Wiggington the answer? Yes if you compare his approach to that of Morgan Ensberg. See, when Pence was hitting #5 I suspected that Houston was going to be in trouble because of his propensity for striking out a lot. But Pence hit for high average so it made for good run production from the lad and made Lee's two strike approach very viable. Pence picked up the ducks that were on the bases that Lee would push over into scoring position (because on their own, those guys were unable to score on Lee's singles or doubles). Can Wiggington do the same? Well several things to consider: Wiggington does hit for average and has pretty good power. That is a very good combination, right up there with Pence's makeup. Perhaps not as high an average as Pence (so far), but good enough. And Wiggington does look like he can generate some pop perhaps a little more consistently than Pence. I like the prospects of this, a lot. But Wiggington is a dead pull hitter, which is not a bad thing at Minute Maid but could be limiting in other parks. Pitchers are coming inside a little more at Minute Maid and once Wiggington gets a feel for what the NL pitchers are trying to do to him, he'll learn to look for the inside pitch in certain situations and that homerun on Sunday may just be foretelling of things to come. What would make Wiggington a deadly #5 is if he learns to go to right field more with solid line drives. Pence did that well, Lee does that really well. Alou was a master of hitting the ball from gap to gap, with the ability to turn on inside pitches still intact and driving the ball well into the CBs and beyond. Alou was perfect for both the Dome and MMPUS because of that. If Wiggington learns to handle outside pitches, he'll do the same. Will he or can he? I dunno. I've watch a sparse few times when he's hitting and it does seem like he does not handle the outside corner as well as he could or should. But again, it's a sparse few times I've watched so it will be fun to watch this team for the rest of the season.
Leadoff, #2, #5 and #6 are keys for Houston. Don't let the pablum talk from the nutless worms in Houston divert you from these keys when they talk of Everett and Ausmus. Any talk of Bruntlett or Towles being key is just plain silly talk and should be appropriately dismissed.