Personally, I would avoid 1915 for the reasons stated by others ... not enough French squadrons in action. I am currently flying a German career in the fall of 1915 in Verdun and have flown 30 missions without seeing even one enemy plane. There are essentially no French fighters, and hardly any two-seaters prior to 1916 so you have the sky to yourself.

Do we necessarily need to have the WOFF dates and real-life dates match? Seems it might be easier to let people just fly at any time (like most people already do in WOFF), then there is no worries about missing days or weather cancellations. No big deal either way.