Ray Hare said:
The reason I mentioned religious relics is because they are somewhat based in reality and combining them with The Twilight Zone twist gives people a tangible connection to relate to...not just silly aliens...
As far as I'm concerned religious relics and the Twilight Zone spring from similar imagination: figments of fiction constructed to tell a specific story often with a moral purpose. Then there are those relics created by religious orders to attract revenue from fee-paying tourists (i.e. pilgrims).
It's what Captain Blumburtt would refer to as "all that mumbo jumbo rubbish". However, in Indy's world we know, and he knows, that some of the mumbo jumbo hocus pocus has a reality. The silly Ark was just as real as the silly aliens.
For me the power emanating from the Ark required just as much a suspension of disbelief as the aliens. The next film could have Thor's hammer or Odin's toothbrush, but it's the quality of the story that matters, and that's what makes them real in Indy's world.
There was nothing really wrong with the aliens themselves, just in the way that they, and other elements of KOTCS, were handled.
A Twilight Zone style twisted tale of mystery could be the perfect vehicle for an investigator of more mature years. The artifact in question could be anything.