The point is that I can't decide what other people should value culturally. And I certainly shouldn't send in mercenaries to "secure cultural artifacts".

It would be acceptable to offer to buy the ones you intend to preserve, or to donate to a museum to preserve the ones they see as important. Archaeology at gunpoint isn't good for the artifacts, isn't good for the people who had them, and isn't good for the people that take them. The best you could do in that vein would be to create a new cultural artifact featuring an adventurer-archaeologist that pilfers the important artifact you would like to preserve as the main plot MacGuffin. And to not make it about stupid crystal-skulled aliens.