So now if I understand this if I buy a New Modal X I can have it when I purchase it as 70D and if I want at a later date upgrade it to 100D for about $8,000
Historically you’d pay a penalty for a software unlocked feature not purchased as part of your original order. I’m not sure what the battery unlock will cost later. I’d recommend getting a written commitment from tesla with the unlock fee applied after delivery.
Check the actual size of the battery. Turn the wheels and look at the label on the pax side of the battery. If it is an actual 100 that is software limited to 75, you can get it upgraded. If you have to swap out the battery, you are out of luck.