This also reminds me what a mistake Google did when they didn't buy Palm. They could've paid only $1.2 billion for their huge mobile patent chest (probably about as big as RIM), their WebOS technology, which I'm sure they could've used, and also 1000 employees, where many of them were engineers. Palm would've been a total bargain for Google.
With RIM, Google has 2 strategies:
1) Get them now by spending 1/3 of their cash, and immediately switch the company to Android. If they move it fast and do it right, they have the opportunity to make Android bigger in enterprise than iPhone will ever be. With RIM, they also have the opportunity to make a lot of money from hardware - maybe close to what Apple is making. The downside is some Android partners may not be too happy about this, but as long as they remain fair towards them and give them access to Android no later their their own RIM division, I don't think they'll mind it too much. They'll still want to use Android because Android is still the most popular smartphone platform they can use by far, right now. It's not much different than if Microsoft bought a PC manufacturer.
What I'd love about it as a consumer, is that there would be a strong manufacturer, Google's no less, that will make great stock Android smartphones.
2) They can let RIM collapse, and buy them in 2013 for much less just for their patents, maybe for 2-3 billions or so.
Either way they have to take into account that others, like Microsoft might bid for them, too, although I'm not entirely sure Microsoft will buy them right now, after their partnership with Nokia. And at least Android has 50% market share, while WP7 has 1%, so Microsoft's other partners besides Nokia might leave them altogether. And then if Microsoft can't turn WP around with the fast declining RIM, and the even faster declining Nokia, they're gone from the mobile space, and they'll take both RIM and Nokia with them. Google buying RIM at its peak is one thing, Microsoft buying it when WP hasn't even become larger than WebOS, is quite another. Why would the others stick around for an OS that doesn't bring them any significant sales, and when Microsoft will play strong favorites with Nokia and of course RIM, which would be theirs?
Perhaps they could arrange a coalition of their own, involving IBM, or one of the other phone manufacturers as the ones who would take over the actual phone business...
They need to set up a patent pool with their Android partners, and then start bidding together for other patents as well. This would probably be the most effective strategy that they can relatively quickly implement.
As for buying RIM together with other companies, I suppose Google could spend a big part of their money to buy it, and then they'll sell the hardware division to Samsung or whoever, the other divisions to other companies, and keep only the patents for themselves. But they'll have to make the deals prior buying RIM, so they can make their money back later.