Sorry, I'm slightly dumb when it comes to some of the baseball stats, or hell not even slightly, but how does the fWAR work for Fowler if he's coming back? Isn't it a stat against himself? Or I guess since he's changing positions it's his stats over that position last year or something? So, heywards stats increse over fowlers, and fowlers over who is being pushed out from last year gives you the aggregate increase or something like that?
Well I just took the fWAR totals each posted last season and added them together assuming they were all FA's since they technically were. As to how it "improves" the cubs it sort of depends on a number of factors chief among them who starts. If you go
here you can see projected fWAR totals for all the cubs and the thing on the side has combined team fWAR. It's not 100% 1-1 total for wins but basically the projection thinks the cubs are around a 100 win team. I believe the "replacement level" team is estimated to win 47 games so if you add that to the 53.6 fWAR the cubs have you'd get 100.6.
I don't off the top of my head remember what it was prior to these moves. probably just the difference in Cogs projection vs Fowler's is all that changed. As for how the different positions change things, I'm not 100% sure myself. I do know for a fact that the defensive portion of fWAR is position based. So, if you're projected to be say a plus defender at LF it's not as valuable as a plus defender in CF. I also believe the batting portion has a position based factor in it as well though it's not that big.
All that being said, from a pure hitting standpoint Fowler is possibly being oversold. Don't get me wrong, I love the move it's just that you're essentially swapping Fowler for Cogs and from a hitting standpoint the value isn't much. Where I think you see the value is that as I've said on here before, if Heyward had gotten hurt you're a lot worse off than you would be now if Fowler or Heyward gets hurt simply because Cogs, Schwarber and Soler can't play LF. Fowler and Heyward essentially have you covered there now and if the worst happens you still have Baez. It's just a better overall fit of parts even if Cogs was a really good hitter.
Also, if you have any other WAR questions feel free to ask and I'll answer to the best of my knowledge.