Are "wider" battery packs less at risk for polarity reversal?
The biggest problem with this design concept is that cells in parallel automatically have the same potential at their terminals. It doesn't sound like a big deal, until you consider the possibility that one cell can short out with age.

Normally, a shorted cell just loses its voltage and becomes ineffectual. If it were side by side with a similar cell, however, you have essentially guaranteed the loss of the other cell as well.

Cell reversal occurs after the cell is totally discharged, causing it to develop an increasing voltage in the wrong polarity. Having another cell in parallel won't help, since it has no choice but to discharge to the same voltage as the dead cell, which could actually set up a circulating current between the two cells. 

Best battery practice is still to stack up cells to get voltage, then stack strings to get current. No one talks about it much, but this has the advantage of putting the cells internal resistances in the path of parallel problems like this.

Side note: technically LiPo and lithium batteries don't require access to intermediate voltages, so much as it is just a very handy way to charge the battery much faster, or get other voltages into a device. Having access to every cell means you can charge and monitor them all indepedently, too.