Well first of all the best way to give young drivers chances is obviously increase the number of teams to 15 (26 in the race, 4 not qualifying) but as the FIA seems fine with current teams blocking out potential competitors (madness) that's unlikely to happen soon with the sharks in charge of the sport.
Other ideas:
*** - Increase the number of rookie Friday practice testing days to at least 6 instead of 2. Two is ridiculously few opportunities considering we will have 24 GP's next year.
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*** - The teams do 2 full days of Pirelli testing each year. And they use their race drivers for it. Force the teams to use rookie drivers.
This year AlphaTauri and Alfa Romeo did 2 days of Pirelli testing at Imola. Ferrari one day at Imola and one at Mugello. Alpine tested one day at Imola, don't know where else they tested.
Red Bull tested a day at the Red Bull ring together with McLaren and a second day in Monza. Don't know where Mercedes testes (Silverstone?).
Haas was the only team who at the beginning of the year said they wouldn't participate (Schmacher did Pirelli test for them last year) but it seems they still might do so in Mexico City.
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In the past (early 2000s) both Michelin, Brigestone and Pirelli acquired a car and hired a driver themselves to test privately:
Were hired by Michelin to test for them:
- Max Wilson (Bra) & Tom Kristensen (Den) did Michelin tyre tests for Jaguar in 2000.
- Jörg Müller (Ger) did Michelin tyre testing in a Williams in '99 & 2000 (he was also rumoured as a possible Williams driver for 2000 btw)
- Tom Kristensen (Den) also tested for Michelin in that Williams in 2000
Between 2010 & 2012 the following drivers were hired by Pirelli to test tyres for them
- Nick Heidfeld (Ger) in 2010 in a Toyota
- Romain Grosjean (Ch / Fra) in 2010 in a Toyota
- Pedro de la Rosa (Esp) in 2010 & 2011 in a Toyota
- Luca di Grassi (Bra) in 2011 in a Toyota and 2012 in a Renault
- Jaime Alguersuari (Esp) in 2012 in a Renault
Were hired by Bridgestone to test for them:
- Aguri Suzuki (Jap) 1996 in a Arrows Footwork and a Ligier and in 1992 & 1993 in a Tyrrell
- Jos Verstappen (Ned) 1996 in a Arrows Footwork and a Ligier
- Tarso Marques (Bra) 1996 in a Arrows Footwork and a Ligier
- Damon Hill (GB) 1996 in a Ligier
- Christian Danner (Ger) in 1990 and 1991 in a Reynard (-Mugen) : that F1 car never drove races, Reynard used those tyre test to prepare an F1 entry that never happened. For years Reynard postponed F1 entry, same for Japanese outfit Dome who tested an F1 car a lot (mostly with Apicella behind the wheel but never entered
- Marco Appicella (Ita) in 1990 in a Reynard (-Mugen)
- Paolo Barilla (Ita) in 1989 in a Reynard (--Mugen)
- Heinz-Harald Frentzen (Ger) in 1993 in a Tyrrell
- Johnny Herbert (GB) in 1993 in a Tyrrell
- Mauro Martini (Ita) in 1992, 1993 & 1994 in a Tyrrell
- Volker Weidler (Ger) in 1990, 1991 & 1992 in a Tyrrell
(The drivers who tested for Dome in 1996 were Marco Apicella (Ita), Michael Krumm (Ger), Naoki Hattori (Jap) & Shinji Nakano (Jap)
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*** - Bring back the rookie 2 day test session at the end of the season (it seems that was scrapped in favour of Friday practice which gives rookies actually less total mileage).
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*** - Organise two rookie races (so 22 GP's + 2 rookie GP's with world championship points counting so a rookie could decide the constructor championship with only rookies or drivers with a maximum of 6 races in F1.