I think he is not talking about make a foreign player national, but a national one buyed with 18-19 years considered as domestic (as adquired in draft) when he arives to 25-26 y.o. I agree with this, sometimes you can not draft what you want and having more merchandising benefits just for training draftees it is not fair because it depends too much on the luck you had in draf when starting a new training plan.
5 years seems too much for me, 3 or 4 would be ok.