Does he have a car racing licence though? The FIA don't give International A/B (I'm not sure which is the required level) licences out like medals at a politically correct sports day.
Rossi has the racing licenses, he does a lot of rally and usually does the special rally events that take part on normal racing tracks, he also started out racing karts as a kid, then switched to bikes because he didn't have enough money to compete in karts. He has tested an F1 car before too, being about 6 tenths off Schumachers pace, something I doubt Vettel could do given the same chance and same amount of practice.
For being 0.6s off Schumacher's pace, don't put too much weight into that. It's a publicity thing more than anything else. Lap times during tests are completely meaningless without taking into context the car setup, fuel load, and tyre compound. Quite a number of drivers on the current F1 grid - including Vettel - could do the same, if not better. I'd wager even someone like Sebastien Loeb or Andy Priaulx could have a 50-50 chance at it.
It's probably Grade B.
Grade A is for F1, GP2, IRL, and any other races listed in the FIA International Calendar (A1GP is not listed).
Grade B is for WTCC and GT, and again, any other races listed in the FIA International Calendar, or deemed appropriate by an ASN (a national motorsport governing body).
Grade C is for auto/rallycross and trucks.
Grade D is a special license for non-license holders, subject to individual approval by the FIA.
Grade R for road events like road rallies.
A private test with Ferrari is one thing, but official tests and getting a racing seat is another.
Rossi will need to obtain a Grade B license and compete and be classified in at least 5 races requiring a Grade B license within the past 24 months. Then he'll need to obtain his Grade A license. Then he'll need to either:
- Complete a 300km test at racing speeds in an F1 car, and prove to the FIA that he has an exceptionally good record to be fit to race in F1 (the Super License will then be probationary for 12 months, and reviewed every 3 months - this is how Yuji Ide got and lost his license, and how Kimi got his).
- Classify within the top 3 in the GP2 series, or GP2 Asia series, or Formula Nippon, or IRL.
- Win the championship in F3 Euroseries, or British F3, or Italian F3, or Spanish F3, or All-Japan F3, or World Series by Renault.
If he really wants to race in F1, he'll need to eat a humble pie for a year or two first. Unless if the FIA is willing to break some rules and make an exception for him (pretty silly, IMHO).
FYI Vettel could barely get within 6 tenths of Kubica when he was BMW's friday driver, and thats someone with single seater experiance who is meant to be the next Schumacher. So getting within 6 tenths of Schumacher in his first drive in a single seater of any kind is pretty good, especially considering it was an old car and probably not using the optimum setup.
I'm not saying he would beat these guys in a proper race, just that he is more than capable of performing well in A1GP if he chooses to race.
I wouldn't be so sure. Generally speaking from all the times I've ever seen "freindly" cross over competitions between motorcycle and car racers the motorcyclists have done a lot better in the cars than the car drivers have done on the motorcycles. You need to have a highly tuned sense of what the rubber is doing on the road to be fast on a motorcycle.. far more than you do in a car I suggest. I'd say fast motorcycle racers are probably more tuned in to the feedback from the tyres than a lot of car racers are.