Just filling out the sideboard of a CT deck and wanted to get some feedback on strong sideboard cards that can play double-duty vs. Progenitus and Merfolk decks. After searching on Gatherer, the best I could find is Llawan, Cephalid Empress and Meekstone.

Vs. Merfolk, Llawan seems like a fucking beating. They either have the Daze or Force to stop it or kept you off the mana to play it, but it trumps their deck if you can stick it. Vs. Progenitus, well, you need to get it off before you're dead. Costs the same as Natural Order. Also, beats for 2.

Vs. Merfolk, Meekstone is infy easier to play than Llawan, but requires they have 1 or more lords (not unreasonable) and that you can catch them with their pants down. Problem is they can build up and alpha-strike if you can't put the game away. Vs. the big guy, you're still taking 10. Also, Grip. They're everywhere. On the other hand, Meekstone is useful vs. more opponents and can reasonably come in vs. other decks that aren't Merfolk.

So, Llawan seems like a good choice, given the above, though I thought I'd ask the community if I'm missing anything.