That would be the tail wagging the dog! If the right sized major unit is a 16 aircraft Squadron, then the primary unit for operations should have 16 aircraft. But as long as such units are sub-divided into flights, then why not give those flights historic numberplates and since they are commanded by Squadron Leaders, and the bigger units by Wing Commanders, particular designations would seem to make sense.
The Army have done it by cap-badging Battalions, the French do it, and we have arguably the most historic fighter units of the RAF facing disbandment, number-plating training units, or already consigned to oblivion.
With numberplates for Flights you could 'bring back' 19, 92, 56, 74, 41, 54, 208, 17, 20, 35, 50, 83 and even perhaps 249.....