Basically I think Bale will never return to the left as he doesn't get enough goalscoring chances there. The main 2 options that remain either stifle the team to accommodate Bale (the current 4-4-2) or require 2 new signings and the exclusion of Lennon from the first team (the mooted 4-3-3). IMO 4-3-3 more evenly distributes the burden of goals while keeping Bale in a position to score frequently, potentially maintaining his goal output but increasing that of the rest of the team. Also I think it's worth pointing out that Bale is not brilliant in tight spaces and hence can seem a passenger in tight games when deployed through the middle.