About employing French : French Emigré officers, especially engineers, were in English pay, in addition to the Royal Emigrés regiment. Navy Board also recruited a French engineer, at gret expense, to improve ship design. But they were deceipted by a second-rank engineer, who produced few effective work.

So nothing dashing or original in employing Phelippeaux.

I think you are making a sweeping conclusion with insufficient facts.

As far as I can see, it was extraordinary when Sir Sidney Smith's employed a number of his French compatriots in his dashing adventure to stop Buonaparte in the Levent. Please take note that this was a military mission against the French army, not some desk job in London. So, please provide some other example of a French officer commissioned into the English Army or Navy then going into battle against the enemy tasked with a most critical job. I maintain you can't, but, would love to be proven wrong on the point, unfortunately what you have provided so far does not do that.

It can be difficult to prove the something was never done but in this instance, at least with Nelson, we can;

The Dispatches and Letters of Vice Admiral Lord Viscount Nelson with Notes by Sir Nicholas Harris Nicolas: January 1802, to April 1804. Henry Colburn, 1845

p.237-238

TO HIS EXCELLENCY HUGH ELLIOT, ESQ. (English minister to Court of Naples)
Victory, October 8th, 1803
My Dear Sir, . . . I assure your Excellency, that I would not, upon any consideration, have a Frenchman in the Fleet, except as a prisoner. I put no confidence in them. You think yours good: the Queen thinks hers the same: I believe they are all alike. Whatever information you can get me, I shall be very thankful for; but not a Frenchman comes here. Forgive me; but my mother hated the French. I am ever, your most faithful and obliged, NELSON AND BRONTE.