I think it is a good idea that will slowly gain traction as the fans associate a number with a particular driver and perhaps a sort of 'cult' following will follow.
There is a tradition in sport in the USA that when a 'star' sportsman retires, or dies, his number gets retired from the normal roster of those available. Just last week the number '2' was retired from the roster of the New York Yankees baseball team in honour of the recently retired star, and one of the best players ever to play the sport, Derek Jeter.
A look around any baseball, NFL, basketball, ice hockey stadium in the USA sees many numbers hanging in places of honour and all those numbers are 'retired' from that stadiums home teams roster, never to be used again. Perhaps that will eventually come to pass in Formula 1 although in the future the supply of numbers will surely dry up.
Many numbers in motorsport are still synonymous with drivers albeit unofficially.
In NASCAR racing in the USA the number '43' will always be that of 'King' Richard Petty and that car number is now used on one of his team cars driven by Aric Almirola. The number '3' will forever be associated with Dale Earnhardt, '24' with Jeff Gordon and so on.
In MotoGP I am not sure there will ever be a more famous number than the bright yellow '46' of Valentino Rossi.
In Formula 1 the numbers, up until the 2014 season, have moved between drivers but 'red 5' will always be associated with Nigel Mansell and '27' with Australian World Champion Alan Jones certainly, but primarily and most famously, tragically even, with the Ferrari of the late Gilles Villeneuve. In 2017 those numbers are used by Sebastian Vettel and Nico Hulkenberg respectively.
Today's Formula 1 drivers chose their own permanent numbers for varying reasons. Many of those drivers, like World Champion Lewis Hamilton and Red Bull driver Daniel Ricciardo, chose the number as a reminder of that which they had on their very first racing experience in a Kart. Some, like the now retired Nico Rosberg for sentimental reasons (his Father Keke's number), others for commercial reasons. Valtteri Bottas, or perhaps his advisors, chose '77' because of the marketing possibilities associated with that number and the 'TT' in his christian and surnames.
As you might expect Kimi Räikkönen had a less than emotional reason when he chose his number '7' saying "It's the number I already had last year and I saw no reason to change it."
With the drivers of today's Formula 1 cars hidden low in the cockpits and many of the helmet designs, if you can actually see them in the car, looking similar due to the obligatory team sponsors logos, as well as the cars of each team, by regulation, having an identical livery, it is only by the numbers that anyone other than a dedicated fan can actually pick who is driving.
The FIA, or perhaps new F1 owners Liberty Media, have attempted to address this issue but more must be done. There has to be an area put aside on each car specifically reserved for number and name of the pilot in the cockpit.
That will be difficult to achieve with the cost of advertising space lost to a team, even for the smallest recognisable area, being in the millions of dollars. Perhaps the FIA could even buy the required space from each team then charge the team an extra couple of million dollars extra for the licence to race.
A more simple idea would be to take a leaf out of the rule book for New Zealand's own Toyota Racing Series (TRS) and have not only the clear driver number on the front of the car, as it is now, but also the top rear corner of the rear wing in a representation of that drivers national flag.
Liberty Media are making huge strides already to make the sport more 'user friendly' to the fans so I am sure that if they really wanted to they could achieve the objective.
It cannot be that difficult, can it?
Seems to work in the TRS.