I think you're wrong (and weingart) on two things above:
1) Patients with pure hypoxic respiratory failure do benefit from IPAP. Yes, it is the EPAP that helps address the hypoxemia, but (essentially) all patients with pure hypoxic respiratory failure (from an elevated A-a gradient, I.e. The ones you'd be using NIPPV for) will get tired and benefit from a touch of assistance.
2) Give the patients with severe auto-peep all the epap you want, it won't hurt them. Applying an artificial amount of Epap/cpap/peep that is below the intrinsic peep will have no effect on ventilation. In fact, if a patient who is autopeeping and having difficulty initiating the breath, the appropriate thing to do is actually raise the e-peep to approach the I-peep such that the patient becomes more synchronous. Sure, they don't need it on bipap, but you're not hurting them.