It's an interesting thought. I'd disagree with the notion that the phonetic alphabet recognizable to military comms today wouldn't remain more or less recognizable in the 31st century, but I would agree that a millenium of linguistic shift certainly could mean that some changes would be realistic. Problem with that however is we don't really see evidence of linguistic evolution in the fluff (the Clans' made up words notwithstanding). We DO however see that there is some variance in phonetic alphabet usage in the BTU from the NATO standard. Able instead of Alpha, Baker instead of Bravo, etc.
I love your idea, so please don't take my criticism as being mean spirited. But, a couple of thoughts I have about your Noruff Phonetic Code:
Some of the WWII phonetic letters that are in use in the BTU that predate the NATO alphabet might be explained as being the SLDF standard rather than being "pre-NATO" designations. In line with this, the ELH's phone book entry (in the original Merc Handbook) seems to uniformly prefer Able/Baker/Easy rather than their NATO counterparts, and that would jive perfectly with originating in a SLDF Noruff Phonetic Code. I'm more of a "old books mean more than new books" kind of guy, and haven't really digested the FM:SLDF volume. That'd be a very interesting experiment to see if that still jives.
Kerensky for K: I can see a Clan variant on the Noruff Phonetic Code making use of this, but I'd still kind of expect not. They made a hard break from their SLDF origins, and their embracing a neo-Greek(perhaps Spartan?) convention is a prominent part of that. (Alpha, Beta, Gamma, etc) Besides, he/they're too hallowed for such mundane communications usage. And if not, there's also the problem of units of credit also being called Kerensky. If a clanner says "Hey I have Kerenskies here", there'd be ambiguity as to whether he's talking about money or something else that begins with a K as an abbreviation. At any rate, if the Noruff code is supposed to go back to the early SLDF, then the chronology is all wrong for the Kerensky name to have any importance.
Dovetailing on K, some words are SO common that they'd have the same "are you using a letter designation or really using that word's common use?" ambiguity. The military's common usage of TANGO to mean "target" could certainly evolve into TARGET simply becoming the phonetic word for T, some other ones seem to needlessly inject way too much ambiguity into communication. A lot of your words will be in regular use in comms, to the point that certain acronymns being spelled out can also be a plausibly sensible phrase or clause of a sentence. That's a bad thing for clarity, which is the point of the phonetic alphabet in the first place. It's not JUST about being words that can be easily extrapolated if part of the word is unintelligible over the radio. You don't want to hear "dropship fleet" or "PPC heat" come thru over the comms and have to figure out if that's a literal reference or an acronymn being called out.
UNIFORM and VICTORY: Just puzzled on these. It makes sense that some words might be retained in the Noruff code from the NATO code, so sure why not UNIFORM. But if that's going to be the case, why make VICTOR less brief by adding the extra syllable?
ZENITH and NADIR: Actually no criticism, I just wanted to say these are brilliant. NADIR shaves a syllable off of NOVEMBER, plus the importance of these concepts in military movement make for a natural/organic evolution to the phonetic alphabet.
BRAVO ZENITH! (I think that just made it into my headcanon)
A couple of suggestions with my criticisms in mind:
A: I actually do really like ARES, given the prominence of the Ares Conventions in-universe. Still, I think there may already be contextual evidence that the SLDF liked/used ABLE. Perhaps you can keep ARES and say Able was just used in unit designations rather than in the phonetic alphabet.
C & S: COMPUTER and STAR are just going to be said way too often in reference to actual computers and stars (the stellar objects, not the Clan force structure) to have arisen as viable phonetic words, imo. (suggestion for alternatives to come)
D, F, & R: DROPSHIP, FLEET, and REGIMENT are also imo going to refer to their respective common words way too often, but have the added problem of being extraordinarily catastrophic if you mistake them for being phonetic words. If someone says "lookout, dropship fleet overhead!" and you take it to mean some aircraft purged a "dookie flush" from its lavatory, that's super bad. (suggestions to come)
G & O: GUN and OLD seem prone to falling victim of being unclear if the entire word doesn't come through loud and clear. Perhaps GAMMA and ORBIT as alternative?
P: PPC could work, but there's a certain amount of inelegance in using the word (too many stops). I'd suggest PARSEC in PPC's place.
A crazy idea: I'm not sure I like it myself, but it DOES fit very, very, VERY well as feeling "in-universe". KURITA, DAVION, STEINER, LIAO, MARIK for K/D/S/L/M respectively. I think K D & S really should have replacements, and LEAGUE for L is imo iffy about clarity over the radio. Problem is I like MYOMER for M... but if you go with most of the other great houses, you just have to do all 5 :) It may introduce the sort of ambiguity I'm otherwise arguing against (hey, did you mean those are KURITA forces or Kurita forces?) but my gut tells me it'd still work. Plus, it does jive exceptionally well with the existing naming conventions for unit variants. XXX-#D mech? You don't have to call that a DELTA/DROPSHIP variant, it makes perfect organic sense to call it a DAVION variant.