IMO rallying has got too fast and far too expensive, this is mainly due to the shortened rallies meaning drivers are pushing far too hard and creating a stupidly high risk of having big (and if it doesn't stop often fatal) crashes. Don't forget Group B cars were dramatic but not that fast, no where near WRC pace. I think much more standard cars on long rallies that are proper endurance tests is the way to go.
Group B cars and other insanely fast specials will now have to be relegated to rallycross/hillclimbs where they can run in comparitivley much safer conditions. As a new generation of Group B cars would not only be spectacular but genuinely blisteringly fast and removing active diffs/TC is never going to happen.