I used to wear LL Bean all the time when I was a kid but haven't purchased anything from them in years, as their fits are traditionally huge and boxy. At the same time, I would never pay $200 for a plaid shirt; I don't think most Bean customers would, either. A Signature line would occupy a very happy middle ground.
A few thoughts, though ...
1. What the hell took so long? Lands' End has been offering tailored fits for years now, and they've proven popular. Several old-school brands have jumped on the fashion bandwagon a while ago (Woolrich, Wolverine, etc.)
2. Will slim-fit plaid shirts and buffalo jackets prove popular beyond the current Americana fashion trend?