I would also have interest in this one as an all rounder, but given the price tag for those "I Want" lenses, once again another cure for G.A.S. is coming.
BTW, I do a massive amount of auto racing as well, but only sports cars, I.E. IMSA, Le Mans stuff. When I did Watkins Glen 6 hours this year, I shot about 3500 with my EF 400 f/2.8. The 2.8 allowed me to shoot through catch fencing and not see it in the photos. I probably did 200-300 with my 100-400L mark II, and maybe 4000 or 5000 with the 70-200L Mark II. I did not have an exact purpose for that lens until I got it and found it's sweet spot. I shot nearly 10,000 track & field meet photos with it too. I used the 24-70 maybe 20 times. So far the 70-200 wins for racing.
One other observation I could not find where to add, so it goes here. I might have seen 2-5 people with the R3. I saw a huge number of regular Joes like me with 1DX models. Probably hundreds to maybe even 1000 with the R6's I have, but mostly the R5. (Plus a mountain of 90D, 80D, 5D etc. I saw one guy everywhere I went with an 80D, attached to a 500mm with an extender on it. I asked him, are you shooting their nose hairs? If not Sony or nikon, pro or consumer stuff, the R5 ruled, I asked a few pros with the R5 and the 300mm f/2,8 why and heard the exact same answer, "crop". I said, 24 megapixels is good if you have the glass to get it right on the first shot. I do NOT have the time to go through the 12500 shots over 4 days at a race, or 5000 at a track meet, to sit and edit/crop them.