I could imagine, though, that fitting(or cramming, I should say) 3-litre engines to S2000 cars would be either really hard or impossible. So you'd neet completely different set of cars for WRC, which would wipe out one of the major strongpoints of the whole idea of S2000 based WRC: The ability to use the same cars in both S2000 and WRC guise. I still have not heard anyone saying that the turbo would be out of the WRC kit and until I do I will assume it is part of it. How they are going to make installing the turbo to the S2000 engine easier than an engine swap I'm keen to see but even if it would demand engine swap it's still the same car.
The thing about limiting these cars to WRC events only is that it is going to reduce the number of WRC spec cars available to minimum. Why would you get a WRC kit if you can only use it in the 12 WRC events every year? The factory teams will obviously have them and the privateer teams that do most of the events will also get them, but why would anyone else? And if that happens, how are youngsters going to get to drive the WRC spec machinery to get experience or to compete in WRC spec machinery to show their skills against the big players?
The current WRC cars are expensive but because they are allowed in most national championships there are plenty of them around and if one finds sponsorship and wants to rallies competitive top-class machinery it's not a problem. That's because teams like Bozian, Ramsport and PH-Sport have WRC spec cars that they run for money in whichever championship their clients want to take part in. If the use of the WRC spec machinery is reduced to the 12 WRC events every year, of which propably 8 or so are going to be within the working range of these teams, are these teams going to bother getting the machinery at all without having a full year deal for running them on all those rallies? If the kits are cheap, easy to bolt on and quaranteed not to be outdated every 12 months then they might, but otherwise there is no point in getting them to gather dust in the workshop.