By all means there's nothing stopping anyone from expanding the inquiry to all of the languages of Eurasia (or in theory, why don't we just grab everything in the world?). In keeping with the spirit of the inquiry few if any languages would be excluded from the initial "sweep". I only picked those 5 languages because we're most likely to recognize the names.
I guess that the only thing to watch for is for someone to do this research without inadvertently following Greenberg so closely that the work gets dismissed as just multilateral comparison which has its own problems.