A superheavyweight division is not even remotely needed as beyond a certain weight boxers are shit.

Did it escape you that the biggest fighter of them all in Nikolay Valuev was beaten by a guy coming up from cruiserweight and thus one of the smallest?

Beyond a certain critical mass size offers more disadvantages than advantages in reduced mobility. You can't use your size in boxing like you can in MMA. If Valuev could lie on top of David Haye he might have been able to use his size to some effect but as all he could do was punch, (and he punches slower than molasses) he was a relatively easy opponent to defeat. In fact most saw Evander Holyfield beating Valuev as well, another small former cruiserweight fighter, as well as a grandfather and likely brain damaged.

Creating an even bigger weight class would just allow the biggest guys to have a shot of winning world titles that they currently cannot.

Certainly they are not a factor in the division at the moment, in fact most of the best fighters are little guys, Haye, Adamek, Chambers.