How more rallies effects WRC2? with 7 out of 16 rallies in WRC2 - rivals may never face each other, situation sometimes happening now, if it will be 9 or 10 events, not 7 many privateers couldn't afford it, and WRC2 will be another WRC3 with no real championship left. I think best way would be with some iconic events permanent spot in calendar + "they own rules", like night stages, different rally stages km, different number of days, very long legs in Finland, and etc. what was already discussed before + some rotation events with rules, like now - ~350km of stages, 2 and half days, SSS required number and etc.
It could look like this:
Monte Carlo
Sweden
Mexico/(some Africa event)
TDC
Argentina/Chile
Portugal
Sardinia/Greece
Finland
Germany
Turkey/Poland
New Zealand
Catalonia/Croatia
Australia/Malaysia(other Asian country maybe)
Wales

Or something like that.