well i guess it depends on how FB1 ends, it would be good to jump a bit forward, say 5 years, to when our plucky quartet are a bit more world (battle?) weary, makes for a more interesting opener, at the end of the 5th movie, they could push it as close to the Potter timeframe as possible
note: yeah i know they said that the timeframe is from 1926-1945, but if theres one thing thats consistent about the FB production, is that things change and gets pushed further along. heck at this point i'd say, go keep pushing, i'd like to see the ickle future Marauders in some form