I think Miller is overkill for what they need in that pen. If they can get him at a better value than what's out there in the rumors then absolutely, otherwise I'd be looking at Doolittle or Abad from the Twins. Doolittle is attractive in that the contractual commitment is over $10 mil less than it would be for Miller and Abad is a rental.
As far as LF goes I think there are a ton of factors including how Baez and Soler hit over the next month (assuming Soler returns). If Baez continues to show the kind of incremental improvement that he has the answer is obvious because Baez at 3B and Bryant in LF are by far and away the best defensive alignment. Reddick would be a liability in LF but if it was looking like the lineup was short a LF bat, remember that Schwarber was supposed to be that bat with his own defensive liabilities, than I see that as an option.
I said I liked Reddick plus Doolittle months ago. Something built around Soler, Calendario, Vogelbach, and an arm like Underwood makes a lot of sense for both sides IMO. I doubt anyone gives a top tier prospect for either guy and the A's got a lot of depth that they need.
Against Righties
Fowler - CF
Heyward - RF
Bryant - 3B
Rizzo - 1B
Zobrist - 2B
Reddick - LF
Montero - C
Russell - SS
Lefties
Fowler - CF
Heyward - RF
Bryant - LF
Rizzo - 1B
Zobrist - 2B
Contreras - C
Baez - 3B
Russell - SS
Playoff rotation
Arrieta, Lester, Lackey, Hammel
Bullpen
Rondon, Dolittle, Strop, Cahill, Wood, Warren, Hendricks (long)
Bench
Montero/Contreras, Reddick/Baez, LaStella, Szczur, Ross, Coghlan