Can wotc write a license that allows freer 3rd party supplements but makes another company essentially reselling their basic material (pathfinder, etc) difficult or impossible? I have no legal experience, so I don't know.
Well Pathfinder is already done. But if you're asking whether Paizo could do it all again with 5E, I'd say it's not possible to make a sufficiently open license yet not have it allow repackaging of the basic rules.
I don't think that sort of repackaging was ever a problem for WotC until they decided they didn't want to sell those rules anymore. One company in particular made a "pocket Player's Handbook" during the 3.5 era, and WotC didn't even blink. As long as WotC is in the room, no one can compete with them. But as soon as WotC decided to take its eye off the 3rd edition rules, it became open season.
What the OGL means for WotC is that Hasbro no longer has the option to allow the D&D brand to lie dormant. The OGL might have been a shot in the foot to WotC/Hasbro. Actually, let's call it eating the seed corn, because it did produce excellent results at the time. But when times are bad, and when the fickle world of consumer preference turns away from RPGs, there's no option to just put D&D in a vault for 20 years. But it was the best thing the employees could have done, as gamers and as freelancers, because they will continue to have their game supported, and some of them will continue to have jobs. And who knows, maybe they did save D&D, because maybe Hasbro would never have taken D&D out of the vault, not in 20 years, and not in 100 years.