An awesome collection!
I would keep all of them, simply too good and rare to sell any of them now...
I agree in the implicit truth that gen AP parts used for frankens are becoming rare, ironically rarer than the gen watch sold as a whole. But this is understandable as the brand, like Rolex, tightens up its spare parts policy, having gained insights into reps and yes, frankens. The building and circulation of AP frankens will not increase, so you are right, flying tommy owns a treasure trove there.
yet, zoom out on the pic and see the situation in a wider perspective. Any regular visitor at his place will see 6 gen ROOs displayed there. Nobody will have a clue on how much effort, time and money went into building each one. To most if not all of them, he simply went out and bought 6 APs, which requires minimal effort, and plenty of money.
My point is this: The journey of building the frankens is what makes it hard to part with each watch, more than the result of said journey. Each watch is a story which only the builder will understand. If each one was a gen, it will be easy to flip it, and on whim, buy the same model again in the future.