It's easy to envision how you could be allowed to use OSB's to twink, but couldn't for PVP. That level of abstraction is not complex and if you tasked yourself, you could think of many ways to implement it. If they are good or not, is another question, but let's be realistic, it's something that could be done.
One way you could implement such an idea is to have a PVP setting for each character that a player would toggle. Toggle ON would allow you to PVP and do towers and Toggle OFF would allow you to get OSB's for twinking. Changing the setting would wipe your NCU and lock your NCU from accepting nanos that aren't cast from self.