Why MINT and DIVA May Never Debut

Since AKB48 released their 20th single, the second single to include the units DIVA and MINT, there has been some curiosity as to why Akimoto just doesn't make them actual sub-groups.  There has been a handful of sub-groups from AKB48 that've only released one single, but both MINT and DIVA have released two included with AKB's.  Both units have the basic requirement that most AKB units follow: at least one popular/ senbatsu member.  (Nobody knows if they will or not, but) I don't think they will.  So why don't they?

MINT (Maeda At, Katayama, Kasai, Nito, Matsui S)
They have Maeda Atsuko for a center; you could expect amazing sales from this sub-unit.  Plus MINT features the vocally talented Katayama, musically talented Matsui, popular Kasai, and semi-popular Nito.  There are a number of reasons why this unit couldn't debut on their own, besides the fact that Akimoto is producing music for so many groups as is.  I believe the major reason why they won't separate from AKB48 is because Acchan is center.  She is overworked as is, so adding that would just push her to her brink (if she isn't already at that point).  This unit does give the other girls some extra screen-time that they would get if they debut.  Besides Matsui is currently attending college and we don't want another member to graduate because she needs to focus on her studies more.

DIVA (Akimoto, Umeda, Masuda, Kuramochi)
None of these girls are senbatsu for most of their singles, but Akimoto Sayaka did make it into the general election so she counts.  DIVA is home to the super talented members who aren't featured in senbatsu.  DIVA is quite large, but if they were to debut they would be officially just have four members (even though within their two tracks more than those four provided vocals).  I know those who miss old Team K would love to see this group become official because the four main vocalists are all Team K members.  Out of these two units, DIVA is the more likely one to debut, and this would be the best time for them because of all the press anything AKB does gets.  But, I think this unit's purpose was to use the rest of AKB48's members who weren't being included in other part of the single (when MINT was being included).  I think Akimoto liked how it turned out and decided to pull out MINT and DIVA again.  The only weakness of this group is not one member is senbatsu, which means they are not as recognizable.  Maybe Akimoto is including them in singles to build up some interest in them.  Akimoto is a TV show regular and Masuda has done some outside work.  Kuramochi is already in a sub-group though.  What disappoints me about this unit is, not that Amina was left out during the second song, but that while featuring the strong singers they left out Iwasa Misaki (and Nacchi).