Yes, I agree that the Marauder stuff would work best as a separate series. Pretty please, JKR? smile
I quite like that so many questions about the wizarding world (such as the home lives of the teachers) were left unanswered- it means that some fans can have fun making up their own theories and others can find out absolutely everything in the. encylopaedia, when we get it.
If I could change one thing about the series, I'd have saved Tonks as well. Generally I think that what JKR says goes, and I wouldn't want to change it because she's the only one who knows how things are supposed to work out. But, well- couldn't Teddy have had a mum to bring him up?