If the stated aim of genuine inclusion and avoidance of unnecessary offence was indeed the actual aim, and if there was convincing evidence of genuine offence being reasonably taken being addressed by such measures, I think there would at least be a case to be made for it, despite the inevitable confusion which will arise as soon as you dispense with the ability to distinguish linguistically between singular and plural.
The initial problem is that this gender-neutrality is being forced upon us without any discussion, consensus or consultation and we are all being pressurised to conform. Those who object on perfectly legitimate grounds are potentially on thin ice, as we have seen in civvy street where careers, livelihoods, reputations and even personal safety are threatened in order to quell dissent. What sanctions await those in the services who have the bravery (sadly that is what it takes these days) to continue using correct English we shall have to wait and see.
The second problem is a much more serious one. It appears that the RAF - and presumably the rest of HM Forces - is embracing identity politics. This is evident from the drive to gender neutrality - I'm assuming to avoid 'misgendering', which by implication is a tacit attempt to present as a fait accompli the notion of there being more than one gender. We also have seen it in the gradual rise of 'preferred pronouns' on e-mail signature blocks, presumably for the same reason. And we have seen it in the recent furore over recruiting white males - in that case the context was race though, not gender.
Each of these individual issues in isolation is arguably relatively trivial, and nothing to get too concerned about, some might say. It's being done for reasons of compassion, equality, fairness. Who can reasonably complain about that? Take a few steps back and a wider perspective however and the direction of travel begins to become apparent.
The elimination of offence is being presented as justification for changing the ways people have been conducting themselves in relation to one another for centuries, to the extent that, in the case of gender ideology and trans activism, now denial of factual reality is deemed acceptable. If prevention of offence is to be elevated to that extent, then what of crewroom banter, much of which could easily be claimed to be offensive despite it invariably being given and taken in good humour. How will that be policed? Will it be banned? What then of humour or jokes in general, much of which is at someone's expense?
Once the idea that avoiding hurting someone's feelings are paramount, the door is opened to anyone contending anything they wish, no matter how preposterous, and justifying it by maintaining that failing to comply with his or her demands will result in hurt feelings. Once you've conceded the principle that avoiding offence is paramount, you don't have a leg to stand on.
Those at the top haven't thought this through. Identity politics will completely wreck the effectiveness of the armed forces if it isn't stopped.