I'd first comment that I'm a bit concerned with the underlying premise. If I have a supplier so disinterested in root cause and corrective action that they blindly plug onwards (at a constant, bad quality level) with lot failure after lot failure to the extent that they get to the point of rejecting five lots in a row then you want to be rid of them as quickly as possible.
I'd question the usefulness of such an OC curve as having that constant level of devects over time isn't really realistic (you'd hope for some level of corrective action and improvement). Hopefully the only time you'd run into a situation like that would be if you had A supplier with lots of WIP and a process with no monitoring or control; in that case you're gambling anway. Ideally, you'd never select them as a supplier or dump them as quickly as possible. I guess, for comparative purposes it might be an interesting exercise.
That being said, I think this is an easy opportunity for a Monte Carlo simulation (I'd personally use Excel). Build whatever underlying OC curve evaluator you want for each of the sampling plans (Reduced, Normal, and Tightened). Personally,I'd probably just cheat/simplify and assume binomial as there are enough other more important sources of error. Then I'd simulate a bunch of runs and let the accept/reject drive me where it may. Alternately, maybe run until termination length.Tally up the results and assign the value for each point on the OC curve.
Hopefully not too hard or particularly time consuming although your spreadsheet is likely to be pretty large so you'll want to turn off the auto-cLculate function of excel.
My thoughts at 6 am on a phone, good luck,
David