The current Rally1 rules for WRC came from the manufacturers. They wanted to run prototypes, like in sportscar racing, because it was cheaper for them than homologating production cars. Manufacturers outside the current three were also consulted. It hasn't increased the entries, though.
Are you suggesting that ACM (organisers of Monte Carlo) should have a similar say in WRC to that of ACM is WEC? Would that result in a more "manufacturer friendly" rule set?