The best plan they could come up with was to have Damon die? What they need to do is find a way to kill Klaus. That is the ONLY way to save Stefan.
They don't need to find a way to kill Klaus. That implies that the way to kill Klaus is a huge secret. They just need to use common sense.
Any newborn vampire could take Klaus out with ease.
Step 1) Compel your way into the nearest national guard armory.
Step 2) Borrow a Ma Deuce, or something bigger if available. An autocannon would be great. A Mk. 19 grenade machine gun would be perfect. With a vampire's strength, it is perfectly feasable to fire a crew-served weapon from the shoulder.
Step 3) Turn Klaus into confetti. He's fast as hell, but he's not a bullet-timer. His flesh can be pierced and torn, he's just got amazing regen. Machine guns that size don't leave much more than bite-sized chunks. It's hard to recover from that, even with magical immortality.
Step 4) If he starts to regenerate, bury his remains in a thousand tons of cement so that he'll never he be able to claw his way out.
And if that doesn't work there are always tactical nuclear weapons to fall back on. Also, they're not difficult to steal when you have vampire mind control powers.