Well....as silly as it sounds.....Trump would win in November (maybe marginal victory....maybe an overwhelming victory, like 40 states in his favor).
Then you would approach early January, with the arrival of the House and Senate, who might under odd circumstances have a Democratic majority in each (I'm having serious doubts on this angle). The House would meet and disqualify Trump on day one of their meetings. They'd hand this to the Senate on day two, and Trump would be disqualified from becoming President.
Vance? No one says of this situation, but he might say it's a all-or-none deal, and refuse to participate.
What happens on 25 January 2025? Well....without Trump or Vance...the short-term fix would be to appoint the Head of the House (Jefferies).
My humble view of what follows? At least twenty states would refuse to participate in any business....recall their House/Senate members, and massive chaos would occur.
Wall Street? I'd suggest a massive fall in stock values over a one-month period.
It's just a weird scenario to discuss, and would require a bottle or two of whiskey.
I suspect Jefferies would last about 30 days max, and the replacement President probably will be forced to resign by early March.