It depends, I used to run a prohpet and then a remedy as an all rounder but started doing more DHy stuff and found the Remedy a bit uncomfortable for that. But I also did do the odd XC race so decided to get a big bike (dune with 170mm forks) and a lightweight hardtail 29er for the odd trail centre ride/long distance rides or racing. For me, a carbon spicy on its own would probably be all right but if you’re wanting something that can race DH and XC at a reasonable level you’ll be left wanting I think, which isn’t good for an investment of that size!
However, you would have a bike that could do the job of the alpine and 90% the job of the DH bike whist being a hell of a lot more versatile so it might be worth getting one and keeping the hardtail?
EDIT: of course it depends on the relative value of the DH and XC bikes, you could sell the alpine and xc bike and get a zesty/remedy or sell the DH bike and Alpine and get a 160mm bike (and maybe some 170mm forks).