Trading away a guy that is entering the most productive years of his career and doesn't cost much is idiotic (seriously, how much will arbitration cost MN - it's not like he'll suddenly cost them $10 million a year).
It'd make more sense to trade Morneau - he's a good hitter, but he plays the position that is easiest to put a good hitter. He also costs MN $15 million per season. Lastly, by trading him, you pretty much guarantee you can get a top of the rotation starter in return without sacrificing any prospects. The only question is how many pitching-rich teams are there that need a 1B?
Unfortunately, Houston is set at 1B with Berkman, so any attempt to get Oswalt (assuming he'd be willing to come here) would require prospects. I doubt offering Kubel and Slowey would be anything close to what they'd demand.