Thinking out loud…
Maybe it is possible to give different values to some Capitols according to how hard they are to capture:
**Washington: 3 Pts
London: 2 Pts
Moscow: 2 Pts
San Francisco: 3 Pts
Calcutta: 2 Pts
Sydney: 1 Pt
Berlin: 3 Pts
Japan: 3 Pts
Rome: 1 Pt**
And 10 other VCs at 1 pt each.
Sums: 30 VCs points but 19 VCs on the map.
Europe Allies start with 12 VC points (7 Capitols pts +5 VCs )
Washington: 3 Pts
London: 2 Pts
Moscow: 2 Pts
Ottawa, Cairo, Paris, Leningrad, Stalingrad
Europe Axis start with= 5 VC pts (Berlin 3 + Rome 1+ Warsaw 1)
Pacific Allies start with = 10 VC pts (San Francisco 3, Calcutta 2, Sydney 1 + 4 VCs)
Shanghai, Hong Kong, Manilla, Honolulu
Pacific Axis start with Japan = 3 VC pts
Allies start with VC 22 pts while Axis 8 VC pts.
Let’s say Allies need 22 VC pts to win?
Axis need 18 VC pts to win.
Don’t know if this can works but…
It allows flexibility and it is not possible to win if Axis at 17 pts with
Europe have Berlin 3 + Rome 1+ Warsaw 1, Cairo, Paris, Leningrad, Stalingrad = 9 pts
Pacific have Japan 3, Shanghai, Hong Kong, Manilla, Honolulu, Sydney = 8 pts
But, instead of Sydney, San Francisco was captured, then it would have rise to 10 pts + 9 Europe pts: 19 pts an Axis win!
Or, if it was Calcutta for 2 pts instead of Sydney at 1 pt, then Axis would have reach 18 VC points.
Or, instead of Cairo, Axis conquered Moscow or London, 2 pts, then Europe would have reach 10 pts + 8 from PAC, 18 pts a win!
And it is still all 13 Victory Cities win.
At 22 points for Allies, this means, on paper, their is no need to capture a Capitol but it is certain that one side would have reach some VCs. Thus, in fact, a Capitol is probably needed unless being able to push back Axis on both fronts to their initial borderlines, which it is clear they can no more win because of the Allies overwhelming economical resources.
From another perspective,
if Europe goes wrong, and still keeps only his 5 initial points (Berlin, Rome, Warsaw), Japan can still save the day if it captures all 8 Pacific VCs: 13 points. 18 points means an Axis Victory.
While, in fact, it is only 3 VCs+ 8 VCs = 11 Victory Cities win!
On the reverse, if Japan is prisonner on his island (3 pts), Axis Europe can not win even it conquered 2 Allies Capital London and Moscow: 4 pts
(Berlin 3 + Rome 1+ Warsaw 1, Cairo, Paris, Leningrad, Stalingrad) = 9 pts, because it give only 3+4+9 = 16 pts.
But if any 2 PAC VCs are still in the Axis hands, then 18 is reach out for a win.