My damaged wrist nerves would love to try those "butter cups" :- )
Looks like the total cost of upgrade for current ZEB (the only one upgradeable due to chassis sameness bar pressure valves) would be 250 Euro for Charger 3 and 50 Euro for Air Shaft, both of which would come with their respective butter cup.
The travel limitations do start make sense given the current bike slack head angles. There are down country bikes as low as 63 now, it puts a lot of stress on bushings. There a tons of failed SIDs, for which 35mm legs didn't help in slightness, so it's not about torsional rigidity, but all about bushings overlap.
(Still, rather unfair to increase that on Ultimate models only).