"We must finally break these formalities," Berger told Auto Motor und Sport.
"In 1985 I drove for Arrows in Adelaide and the day before did a national touring car race for Bob Jane," he recalled. "It was still possible in those days and everyone had their fun."
Berger is now the boss of the German touring car series DTM, and he hopes Alonso's move to Indy is the start of a new trend.
"I'm sure Vettel would like to do DTM races if he could," said the Austrian. "Drivers today have much more spare time than we used to, as there is hardly any testing."