If we're honest about which rallies are eminently replaceable, I think it would have to be:

Sardinia (which, rumor is, will be replaced next year with an event on the Italian mainland because the promoter hates island rallies. I like island rallies. I'd love to see rally Azores in this slot. If ERC can make it work, and exceptionally well I might add, why can't WRC?)

Poland (which, rumor is, will be replaced next year for "safety" reasons. It would be great to have the Safari back in this slot. The REAL Safari rally, i.e. open roads, 1000km or more of competitive stages, helicopters, all that great stuff.)

Germany (as much as I like all the narrow tarmac through the vineyards, I would trade this for any tarmac rally, e.g. Ireland)

Spain (if this was all tarmac, I wouldn't trade it, but the first day on gravel is super forgettable IMO. I'd trade for a tarmac event like ypres.)

GB (I know, I know, there has to be a rally GB, because... well... not sure why exactly. But you have to admit this is a shadow of its former self. I'd trade it in a heartbeat for Japan.)

Australia (as far as I'm concerned, this is only on the calendar because it's on another continent and the government throws a load of money at it. But it is very, very forgettable. NZ would be better.)