Well, if one were to take this prompt seriously, the platform is going to be defined largely by how it's powered. Newey and crew were able to fit a surprisingly large engine in the very tightly waisted Valkyrie. I like the idea of the Porsche 919 platform with its much shorter engine and a very substantial impact from the front drive electric. You pay a small penalty in total compactness of the bodywork ahead of the driver by fitting the motor and differential up there, but the latter Audi R18 iterations showed a pretty epic capacity to shrink that, though to be honest I just don't know if that level of compactness is going to be accessible for the same level of performance if reasonable
cost is to be maintained. I still think we could get pretty tight.
So Since regs are out, let's say we start with the idea of building a Valkyrie-in-a-shed. So like a tubeframe chassis and building our own bodywork from our own Solidworks model. The first aerodynamic change I would make would be to head in the Praga R1/Allard J2X (and I guess for that matter the R18/ByKolles) direction and build more of the front wing into the space between the wheels and the nose. We could imagine transplanting the APU driven turbocharged 4cyl method of Manic Beattie
into the back and that would give us a significant surplus in airflow that we could use to drive a blown diffuser, in fact if we oversize it a little we could maybe also use it to drive extraction from our heat exchangers. If we went for a bespoke 2L hot-V V4 designed to be boosted to the moon we could conceivably beat the power to weight ratio of an F1 engine in a comparable space at a fraction of the cost, I'm thinking along the lines of the Elmer Thor.
We'd also use 2008 era F1 style wheel covers, and retain the deep channels of the Valkyrie underbody. The gearcase I think would have to be fabricated and use a cassette. Perhaps a carbon case like the 919 could be achievable at reasonable
cost if the oil and bearings are all contained in a bonded-in sheet aluminium sub-case with welded in billet hardpoints.
Conceivably, one could grab a used Praga R1 to use as a basis for this shadetree uber-Valkyrie. I think the floor of the tub is a little flatter than we want to really optimise this, but it's narrow and I think the glasshouse is a little narrower and the price is right. There's one on Racecarsdirect right now for only £125k. Throw in ~£200k for the engine.