Hi Slamfire:
You are correct historically! The 0.473 case head diameter was existence in both the 7x57mm and, if I remember correctly, the 8x57mm cases before the 30-06 was developed. So a more accurate way of saying it would be that the 30-06 was a lengthened and necked up version of the 7x57. At the time I was thinking about how I could create 7x57 brass from 30-06 brass, and not from a historical perspective.
The 2 largest, in terms of numbers, case families are the rimless 0.473 case head, and the belted 0.532 case head. In just the rimless 0.473 case head we have the following partial list: 22-250, 243 Win, 6mm Rem, 250 Savage, 257 Roberts, 25-06, 260 Rem, 270 Win, 7mm-08, 7x57mm, 280 Rem, 308 Win, 30-06, 8x57mm, 338 Federal, 358 Win, and 35 Whelen. This basic head size case is manufactured in 3 basic lengths: 308 length, 57mm length and 30-06 length. Not to mention all the wildcats like the 6.5-06, 25-08 that can be made by necking each length up and/or down. If you are really into case forming all of these can be made from basic 30-06 brass.
The 0.532 belted case also has lots of siblings: 257 Weatherby, 6.5 Rem Mag, 264 Win Mag, 270 Weatherby, 7mm Rem Mag, 7mm Weatherby, 7mm STW, 300 Win Mag, 300 Weatherby, 300 H&H, 8mm Rem Mag, 338 Win Mag, 340 Weatherby, 350 Rem Mag, 358 Norma, 375 H&H, 416 Rem Mag, 458 Win Mag, 458 Lott. This family also has 3 basic lengths a 57mm the 2 short Rem Mags 6.5mm and 350, the '06 length 2.5 inches like the 7mm Rem Mag and the 338 Win Mag, and the long full magnum length of about 2.850 inches such as the 300 Weatherby and the 375 H&H. Again with some case forming you could make any of these from a basic long case such as the 375 H&H.
Stay tuned, and I'll be back tomorrow to continue the long list of cartridges that are both useful and a lot of fun. I'll be starting out at 7mm then.
Have a Good Night, Chat at y'all later.