You indeed can prob. get any biz jet ready in 30 minutes without considering fuel/water/lavatory. 10min to get airside and to the aircraft depending on the location.
Regarding Catering & Cabin preparation however I have my doubts and the IFS needs at least somebody to power up the AC.
If the client turns up early and wants to go with 40min only...yuk! One hour check-in is still rough more often - 90 to 120min is what we have mostly.