Not sure if this has been discussed as an idea. But With the mass amount of FC's in CG and near CG systems, that Never move, Ever, has it been considered implementing a tax for keeping a FC in CG space? Such as doubling the upkeep for every day you are in the CG space over a tick? Thus you can still interact without getting a penalty, but if you just stay parked there, it causes a incentive to move.
Doubled each day could be over a billion credits by the end of the week, depending on installed services [1]. Workable as a deterrent for CG participants if that's what you want - but rather harsh if you happened to park the FC in there, and went away for a couple of weeks during which there was a CG in your home system.
Tying it to the tick would make it much more of a problem for some timezones than others - if you're online over the tick, moving your carrier out temporarily to avoid the fee isn't a big deal but doesn't really free up space in the system. But a rolling 24-hour window for each carrier
everyone could avoid by doing quick hops in and out.
There's several thousand people doing a typical CG, lots of them bring carriers, even with extra charges there'll still be a lot of carriers. Sometimes the CG systems are permit-locked, of course, if you want a change...
[1] Or if you just mean "the upkeep for that day is doubled" so if you're there all week you pay 20 million rather than 10 million, no-one will notice.