Yeah, but at some point you have to pick your poison.
Keep Ellis and you have:
a disgruntled player with pass rushing ability AND you gamble that you'll get great FS play from Keith "Killer" Davis, Coleman, the rookie Watkins, and/or Pile.
Trade Ellis, get Barber, move Henry to FS, and you have:
significantly strengthened your defensive backfield AND you gamble that some combination of Ware, Carpenter, Burnett, the other LBs, Spears, Canty, and Hatcher can pick up the slack that Ellis leaves. And, who knows, with a dominant secondary, maybe you decide to blitz the DBs a little more often.
So you gotta pick one.
Either gamble that the young LBs and DEs can compensate for the loss of Ellis -or- gamble the combination of Davis, Pile, Watkins, and Coleman will yield a great FS play this year.
I've got more confidence in the LBs and DEs.