F1 and the WEC both need to figure out where they want to be in 2025-2030. Both are failing to do so.
Indycar and IMSA have a very sustainable vision, even if it's not earth-shattering. Formula E is building its own thing and laying a pretty strong groundwork while avoiding many of the pitfalls other attempts to start something new have tripped over.
First thing to ask is what do the ACO/FIA want manufacturers to get out competing in their class? Second question should be how much do they value protecting their independent/privateer entries?
In answer to the first question, the aim of nearly the last decade or so has been to develop, learn from and showcase hybrid/electrified powertrains. With the way the automotive industry is going that is unlikely to change, so they should be looking at keeping that focus. That they're walking back a bit on mandating hybrids in this Hypercar class is a sign of how desperate they are right now.
The demise of LMP1-H should be the basis of the answer the second question, they should value protecting and properly equipping the privateers a lot.
Do we really need much more (expensive) development on the aerodynamic front? No, not really.
Do we really need more development on the chassis side? Not desperately.
The answer then to me does seem to be to follow the IMSA/IndyCar/FE model. From all three, have a common chassis (or maybe two or three approved chassis) which can form the basis of every entry. Also from all three, allow manufacturers to develop a powertrain (though in this case ideally hybrid) which can then be attached to any of the chassis. From IMSA, allow manufacturers (or independents) to develop bodywork styling to their liking. Taking from Formula E, have all of these three main areas with a mandatory by rules of entry price-capped supply so that the total cost is palatable to privateers.That puts a common-sense limit on how much am OEM is willing to spend because of the risk that a privateer will beat them on only a fraction of the investment.
That would be following a model that works and one which offers the best chance of unifying the global sportscar rulesets. Once everyone is on the same page, both investment and participation will be less fragmented and perhaps more visionary plans can then be considered.