We can consider that K4 has resisted all solution attempts. Surely the CIA or NSA considered alternatives to English. It is likely standard procedure to compare the ciphertext letter frequency to the known frequencies of the more commonly used languages (they are different by the way). Of course we must consider that government entities would not likely support tying up resources to solve a sculpture that was intended for the employees to solve on their own. This would answer the question many of us have asked about why it’s taking them so long. Also, decryption tends to occur across several groups in a military setting so the odds that one person can do all of the analysis by themselves is unlikely. Almost every employee still holding a job in times like these should form a picture of their boss, from the spooks to bankers to construction workers, and imagine them saying, “Yeah, that’s fine, try and solve it. Just do it on your own time!”
So now we have an opportunity. A foreign language would explain many things: why K4 is unsolved, why English is not an advantage, how steganography was used or suggested by Ed Scheidt, the origin of the inspiration for the Cyrillic projector, why the letter frequencies in K4 are odd and many more.
Am I suggesting the French never tried to read it? Well, maybe… no, no I’m not. It would still need to be ciphered by substitution or transposition. Since all 26 letters of the English alphabet are present, we can assume two things: either the alternate language uses 26 letters or extraneous letters are to be removed which would possibly give a hint towards word lengths. One more possibility, and I will include this under K4 variants as V7, is that a set of A-z letters has been added onto the ciphertext and can be removed.
As with any attempt, we can’t just charge around willy-nilly, we need a plan.