I think we're getting lost in the details. There are many models that work for various series. A common element of the succesfull ones that I see is a form of spending limit, either directly (F1 cost cap) or indirectly (performance capped by BOP so you avoid a spending war for diminishing returns).GT3 was created in the late 2000's by Stephane Ratel using the lessons learned from the FIA GT. He wanted to avoid the spending war that killed the initial GT1 (nobody except Mercedes wanted to continue in 1999) and also make it useless to build "homologation specials" like many manufacturers did at that time. He also banned full works teams and promoted amateur drivers by creating special categories and classifications for them. He recognised that having wealthy amateurs that can race in their own category can help the championship health. Now GT3 has gotten quite expensive for some but Ratel is again ahead of the game and a new GT2 regulation with cheaper and simpler cars (but slower than GT3) has been around for a while and is now gaining traction. So anyone who is priced out of GT3 can go to GT2. There is of course also GT4 as a natural step below. The point for this story is not to apply the same to WRC, but I'm tring to show that GT3 is so succesfull because somebody (in this case Ratel) had a proper long term vision and learned lessons in the past. GT3 is now wildy succesfull and has been for more than a decade, both in high profile international series and lower profile national races.

So my point is that WRC first needs some kind of high level vision of what it should be, not only for the WRC but also the levels below. Then starting from that concept you can decide the details like rally format and technical rules. Unfortunately to me it seems that the WRC has usually been a day late and a dollar short, having to react to something and take some short term decisions with no clear future. WRC was the last major series to add a hybrid and has no clue about hydrogen, meanwhile in the WEC/Le Mans they are preparing a hydrogen class since a few years ago with active discussion with the manufacturers, but I think that's more coming from the ACO (organisers of Le Mans) than FIA. Regarding the WRC the FIA has been asleep as usual.

Now beside the format or cars there is actually another critical issue for the WRC and that is it's "story". Whenever I talked to my friends about WRC in the past 15 years it's usually: Oh that.. well Loeb/Ogier always wins, it's boring. Now it's very difficult to make rules to create a true rivalry because the best will always be the best, however what you can do is create conditions so that there are more challengers coming up. F1 is now also starting to have this problem with Verstappen and viewers are dropping. I think drive to survive helped sure, but the battle between Verstappen and Hamilton was also a big draw. It was a classic old multiple times champion vs young gun, a young pretender dueling with the old king if you will. In WRC the kings die of boredom and the young pretenders are scrapping to get a WRC2 program together to compete in some rallies where maybe they are not even directly competing with the other title contenders. If WRC wants to attract more people it needs a better story.

So to conclude, in my opinion there really first needs to be some fundamental things decided before you go into details. The important thing is to capture the essence of rally and preserve that and then find a format and presentation that works for a larger audience. The danger is that they do the opposite and keep the surface things but change the core - in that case they will lose both the die hard fans and fail to gain new ones.