Yes, Pitching help is needed. But...
Yes, we need pitching. We need help in the rotation, especially, and perhaps one more good arm in the 'pen. We need a pitcher that can pitch deeper into ball games. Ultimately, though, is going out and surrendering prospects the only way to upgrade our pitching?
The difference between good pitching and bad pitching, ultimately, is run prevention. Good pitchers, in combination with good defenses, can increase run prevention. Mediocre pitchers can be helped out by having extraordinary defenses behind them. Upgrading the defense can at least slightly increase the overall run prevention side of the win/loss equation (that being that you have to score more runs than you surrender to win ball games).
While defensive metrics are still not scientifically relevent yet, they're not completely useless either. Upgrading a notably bad, both statistically and scouting-wise, outfielder with one that is better can help the run prevention, and help the pitching.
As long as the difference between the bat that's added and the bat that's replaced is minimal, and the impact on the more-scientifically sound run scoring side of the equation is neutral, at worst, the improvement on defense can make the overall team better. Having a good defense that's less likely to have miscues that extend innings and prevent pitchers from going deeper into games can improve a team's chances of winning. With the extra bonus, too, of possibly allowing pitchers to pitch deeper into ball games.
While I recognize that this idea may be thinking outside of the box a bit for the Mariners, I'd bet that they're at least aware of the principles outlined here. Now, I'm not expecting a change, but I would like to imagine that moving a clearly-ready-for-the-majors Adam Jones into left field, defensively-challenged Raul Ibanez to the DH, and Jose Vidro to the first-bat-off-the-bench would actually help the pitching staff, and may slightly improve the offense.
I realize there are several potential problems with this. It takes out one 'lefty' bat in Vidro, where this team doesn't need to surrender lefty bats. Raul Ibanez also is more comfortable when he's playing the field, and the potential discomfort he may have could affect his hitting. Jones also isn't a natural outfielder, even if he's a heck of an athlete, and while he has learned CF remarkably well, there's always a risk of seeing how well he'd transfer to LF.
I don't see those things as major risks, though. They're very small, really, and I'd actually have Vidro in at DH vs. lefty pitching, and I think he could still get regular playing time. Plus, the type of hitter Vidro is (singles hitter, keeps the ball on the ground, rarely gets XBHs or flyouts) can kill a lot of rallies when he GIDPs. Jones has much more power, and while his batting average may not reach .290 in the bigs right away, there's much, much more to offensive numbers than batting average. I'd be willing to bet that Jones could put up an OPS higher than Vidro's .710, especially when given consistent playing time. And, I'd be willing to be that the pitching numbers would noticably improve, too.
And, you don't have to make a trade to get him in there. Perhaps it's at the cost of Ellison. Nothing against Jason, of course, but I like Adam better. While Ellison actually would be a defensive upgrade, I doubt his bat is any better than Vidro's. And, no way is it better than Jones's...