Simms will draw interest from several teams including Dallas and Miami. IMO, he would be an upgrade over Johnson and he probably would only be here for a year and then be potential trade bait with Bartel or a draft pick being the #2 in 2009.
Garrett would be a huge help to Simms so I would expect Dallas to offer him a backup contract if released. Problem is I don't believe Tampa wants to let him go unless they get something in return. As long as the Garcia contract problems drag out, they aren't going to release him.