If there's a problem with snow on the roads they can't get anywhere no matter where the lifts are, unless we're talking about a chair from the old Devil's Elbow up to Meal Odhar where the snow melts quickly off the south west facing slope....
That basically is the problem in a nutshell with the viability of such a project, a lift up Centre Gully doesn't increase the chances of access for the majority of customers, but would be preferable option from a practical point of view if you wanted a lower level access point. It's relatively sheltered and fairly low level up a gully, so not much visual impact away from the A93 and existing developed area either.
On the other hand a lift up the Devils Elbow side that might be accessible when the slide is blocked, but it's hugely exposed, isn't good for snow holding and would have to dump people in the middle valley or be ridiculously exposed. It would also likely be a red rag to a bull to many because it would be very visually prominent from a fairly wide area!
If the population and customer flow was predominantly to the North of the Cairnwell Pass rather than the South I expect we'd already have lower level access from the road up into Coire Fionn.