Another possible addition would be UE with Mekanism, though these might be seen as just adding extra bagging since it's basically another power system and more thing to work with it a la buildcraft or industrialcraft. The bonus with UE is of course the built in method of power conversion.
I wouldn't mind seeing Mekanism either, and even asked Slowpoke to take a look at the Mekanism mod from UE. His response was, iirc, "No, I will never look at Universal Electricity and it will never be apart of FTB". I don't know the specifics of it, but it is what it is, and his decision...*shrug*