Um if Landon meets Klaus he just might be dead in less than a minute but Landon will be back and Klaus will give up killing Landon in anoter 1000 years.
For you saying Klaus would kill Landon, do remember at the end of TO; Klaus was watching the two dance in the Mystic Falls Town Square and approved of Landon for Hope. So I don't think Klaus would kill him.
I like these ideas one more thing that I would love to see would be the second Tribrid to be born after Hope and of course Hope meeting another one like her and not feeling alone in the world, maybe even a meeting with Valerie would be fun.