I did something very similar back in 2009 with a mk2 focus RS. I called the dealer (Ford garage) and explained due to ‘unexpected delivery delays’ I wished to cancel and request my £1000 deposit back.
The dealer kindly agreed as a goodwill gesture.
Ford had a lot of issues with the engine on those RSs, if I recall, something was over heating and a certain material in either the cylinder head or pistons had to be changed therefore delaying the first batches. Anyway, I’m sure Ford just reallocated this car to another customer as mine was an early order.
A caution to this tale, I then got bored 6 months later and paid over the odds for a pre-registered RS so lost out anyway

I’d think hard about what your suggesting, remember, if you’re considering because you’ve fell “out of love” with the CS 45 due to delays, there’s a good chance if yours is an early delivery in comparison to others, that it may even be more valuable than the price you’ve paid with discounts.