Not sure how you found another new GT-P from Lucid. I thought ours was the very last of the 22'. We owned a 23' GT for 9 months that I base this post on.
The heat pump primarily helps with charging, and I am not sure if anyone knows if there is or is not a heat pump in the GT-P.
The horsepower I personally cannot live without after driving a loaner GT-P for 2+ months (during GT ownership) and finally purchasing the GT-P. Any warranty work puts us in a GT, and I had to drive one for about two weeks about a month ago. The contrast is stark in power delivery and handling. Sprint mode in the GT is equivalent to Smooth and Swift in the GT-P.
As for depreciation, much of the depreciation should be done at 2 years. If you get a 24' and fast forward two years, I do not imagine a drastic change in the depreciation curve before holding steady similar to where the GT-P is now. I do not think many GT-Ps have been resold after the announcement of no more GT-Ps from Lucid, so it is effectively a limited edition trim. I do not plan on selling the car, but this may help the value depending on market response, particularly given Sapphire owners are not likely to sell anytime soon.
Conclusion: Get the GT-P. Depreciation is negligible and at least baked in to the GT-P vs a loss on a new 24' GT. Performance and handling are tangible if you appreciate those characteristics in a car. The worst thing would be getting into a GT-P or Dream-P later and regretting your decision of not purchasing the GT-P in my opinion, particularly if the Sapphire is out of reach.