I would imagine that Geoff doesn't want to do this because TV prides itself on providing freshly mixed juices, but there are also other factors. We as customers have different levels of nicotine preferences, PG/VG, and other special requests that Geoff already accommodates.
I'm just a TV customer, but I think these are some of the reasons.
Happy
vaping, and in the case of TV, good things come to those who wait.