It's still not a commlink. The point of Clustering, as I understand it, is to minimise the size of your active subscription list, and the reason why the devices in a cluster have ratings like a commlink is because those devices can be hacked. The fact that they can be hacked does not mean they can be used to access the matrix.
Ornot, I believe you are mistaken, because it was just to minimize the subscription list then they would have come out and said that. The Dev's said this in the clustering rules (pg 55 of Unwired):
QUOTE
Sometimes, you have a lot of low-powered devices, but what you really need is a single node able to sustain several personas and/or run a lot of programs at once. For this purpose, two or more nodes can be linked together to work as one super-node or cluster with greater processing power.
The bolding is my emphasis of the relevant text. There is NOTHING in the RAW or the fluff to state that Clustering is just to minimize your subscription list
Using the example of the electronic paper again, it can be hacked to display something other than what the user is expecting. Instead of this years predicted profits, it displays goatse p0rn, to the distress of the naive and innocent sarariman trying to impress his boss. It still isn't something you can access the matrix with. That is not its intent.
To counter your argument, I can take a whole lot of Xboxs and cluster them together into a Beowulf cluster with "decent" throughput. Individually each xbox is pathetic, but together they are "mighty"
If you could use other implants as a distributed headware commlink thing then they wouldn't bother charging extra essence and nuyen for a headware commlink. It would be a capacity free addition to regular 'ware. Why are you so intent on saving the 5 or so buildpoints and the 0.5 essence anyway? Do you really need it to make your character so much more kickass?
Well my Chaos Mage has a cluster of his Alpha 'ware to backup the commlink in his cyberhand.