And then I do not think that you should offer a biz jet with a u/s APU to a well paying customer. Might be the last time you see him aboard your aircraft.
Not much of an issue on the Lear-60/60XR. The APU only turns a generator and does not provide conditioned air as PACK does. A GPU (if available) can easily substitute for an inop APU and operate the Freon Air Conditioner. Just more hassle for the crew and ground staff, not for the passengers.