As this point I have accepted that NW is basically Cup Lite and they will both run at the same tracks almost every weekend. If you run most NW races on Fridays and a handful on Saturdays (with most Cup races Saturday nights and occasionally Sundays), I don't think it will affect Nationwide's ratings or attendance much. If anything, I think more Friday night races would help.
The Trucks schedule is what intrigues me the most. They could run a dozen races at Cup tracks, always on Thursday/Friday nights (the night before the NW race). They should also run at least a dozen races at tracks not on the Cup schedule. This is where their schedule has some flexibility. The can basically run whatever time they want. Cup race at Michigan at 7pm Saturday? Cool, have a Trucks race at Nazareth at 1pm that same day. Or, run them at Mesa Marin on Sunday.
Look at all the cool tracks from the Trucks and Busch schedules back in the 90s. I'm hopeful that a lot of them could still support a Trucks race in 2015. The fans get to see racing at more tracks (variety is good for ratings), and local fans at those tracks get to see some Nascar races again. Maybe then we would see a decent TV deal with the CWTS finally getting the exposure it deserves. That series has so much potential, Nascar just needs to capitalize on it.