I never like keeping two arms unless your talking Strasburg and Kershasw that's different. I only advised a big masher like Wills cuz you seem to lack them very much and he's a decent #2 OF with his prodigious power. He's a poor man's (old man's) Stanton and those to me are hard to find.
Your BEST bet is to package Willingham and Halladay for the best keeper you can get I'd shoot for a good young 2b or 3b if you can get any fish to bite. Maybe shoot for Longoria (it would be a risk but would make a great keeper for you go ahead and try it) Halladay still carries a lot of name value AND Longo can't seem to stay healthy. I might consider that package also for Zimmerman as well, but I like Longo a bit better even if it comes with a slightly larger risk (just don't see the love for Zimm - hes had maybe what I consider one top shelf maybe 2 seasons).
The best there is, the best there was, and the best there ever will be!