A cunning plan sir!
Unfortunately, it won't work.
To begin with, the app store policy forbids linking or 'channeling' users to an outside location from inside an app. So MS cannot put a link in the app, or even tell users where to go.
Secondly, the app store operates Apple's notorious 'most favoured nation' clause:
If you offer auto-renewable subscriptions, you can also use other methods to acquire digital subscribers outside of your app. You can sell digital subscriptions on your website or provide free access to content for existing subscribers. In these cases there is no revenue sharing since Apple was not involved in the transactions. Developers keep 100% of the revenue. If you would like to make a subscription offer outside of the app, the same (or better) subscription price must be offered inside the app for users who wish to subscribe from within the app. In addition, you may not provide links in your apps which allow the customer to purchase content or subscriptions outside of the app.
I've highlighted the two relevant points:
1/. If you sell the subscription from your website then Apple does not get a cut.
2/. You cannot offer a cheaper subscription than the one offered inside the application. This means that MS cannot hike the price of the in-app subscription to claw back the 30%.
Even if this were possible, I'm not sure it would be wise. Hiking the price by 30% would probably raise their price above competitors such as Dropbox, in which case I'd just go for Dropbox.
The apps mentioned in the articles used a non-native login and/or a sign up link that took the user outside the app. They were not rejected because they use Skydrive; they were rejected because they broke the app store rules. If they'd connected to their own in-house service they would have been rejected anyway.