I wouldn't do this either - can't move your RB1 w/ what you have behind him & you're solid at WR already - that said, I would try and swing a deal for Bradshaw - Jacobs is always going to be a significant injury risk w/ the way he plays.
Why it is arguable to make the trade or not, I have to say this is another reason why i like bradshaw better..jacobs is an injury risk as well.
I would still make the trade, and then try to trade up another WR for a monster RB ..like combine jones with jennings maybe
I like Bradshaw as much as the next guy - I think he holds immense value.
That said, IMO Jacobs is still the more valubale of the 2 at this point, Bradshaw's value is directly tied to Jacobs health.
Fitz, Smith, Mason, and S. Moss is a pretty solid WR corps - Jennings isn't a need here.
Jones, Parker, Stewart, and Choice doesn't instill confidence as a RB stable...
Jones is stuck in a major time share (and bluntly, has looked awful w/ the exception of week 1 @ HOU)
Paker is hurt - he has turf toe (a devastating injury to a RB), his O line still isn't all that good, Mendenhall is going to steal carries, and Moore is their 3rd down/pass situation back.
Stewart has sucked, Carolina has looked bad, and he's behind Williams
Choice is the 3rd back in Dallas when Felix and Barber are healthy.
Getting rid of Jacobs leaves you extremely thin (at an already thin position).
Now if you could move a RB not named Jacobs + a WR not named Fitz for Bradshaw & Jennings - I'd do that in a hearbeat.