I think that while a 25-race calendar is indeed possible, it would only work if the races were arrayed properly. Something like this:
1 – Australian Grand Prix, Albert Park
2 – Malaysian Grand Prix, Sepang
3 – Chinese Grand Prix, Shanghai
4 – Korean Grand Prix, Yeognam
5 – Japanese Grand Prix, Suzuka
6 – Singapore Grand Prix, Marina Bay
7 – Indian Grand Prix, Greater Noida
8 – Abu Dhabi Grand Prix, Yas Marina
9 – Bahrain Grand Prix, Sakhir
10 – Turkish Grand Prix, Istanbul Park
11 – Russian Grand Prix, Sochi Olympic Park
12 – Hungarian Grand Prix, Hungaroring
13 – German Grand Prix, Nurburgring/Hockenheim
14 – Belgian Grand Prix, Spa-Francorchamps
15 – British Grand Prix, Silverstone
16 – French Grand Prix, TBA
17 – Monaco Grand Prix, Monte Carlo
18 – Spanish Grand Prix, Aragon
19 – Italian Grand Prix, Monza
20 – South African Grand Prix, TBA
21 – Canadian Grand Prix, Montreal
22 – United States Grand Prix, Austin
23 – Venezuealan Grand Prix, TBA
24 – Argentine Grand Prix, Potrero de los Funes
25 – Brazilian Grand Prix, Interlagos
The hardest thing was getting the South African Grand Prix right. It’s very isolated compared to everything else, so I had to run the European leg backwards to finish in Monza. The only problems with the calendar is that Monaco moves away from its traditional place on the calendar and it’ very late in the year for both Canada and England.