The best fig harvest I ever got from a pot was when I left it on top of a full compost heap (out of the way while I started a new heap).
It grew and fruited very fast - the reason being that it had rooted right through the compost heap and into the soil below where it could find water - unlimited supplies for a plant that originated in much hotter climes.
I pruned it that autumn before releasing the pot from its roots to get at the well-rotted compost. Some of the roots were thicker than the holes they had escaped from. Nevertheless, the plant survived perfectly well - but next year (without soil contact) it behaved exactly the same as other potted figs - most of the fruit dropped off.
I now regret I omitted to put it on another freshly-filled heap to see if it would repeat its performance, but I'm fairly confident it would.
Basically this is a well known method called root pruning, but made easier because if the pot is big enough to support the (autumn pruned) tree you can just put a spade under it to remove all that year's roots.
I'm theorising that figs only need root restriction to keep them fruiting when they become big enough and old enough to feel secure - maybe they build up a reserve of energy and become 'complacent'. Root pruning also prevents this - but it is a lot of very very hard work on an established tree - but virtually no work on a potted one...
I've been both very busy and very short of time for the three years since I made sense of this behaviour, (by a whole interlocking raft of unavoidable circumstances) - so I haven't been able to test it as a continuous strategy - yet.
But you get one very good year with no ill effects to the plant afterwards (none that weren't going to happen anyway).
Cheers.
PS. My rich heavy clay is sufficiently restricting to get annual crops from trees planted straight into the (hardest, poorest) soil - good for a decade or so, but they still get to 4m x 3m even with top pruning. When the trees get established enough to stop fruiting it will be easier to just kill them and plant new ones.
PPS. Has anyone tried removing half the biggest, oldest leaves from a potted fig tree before it drops its fruit?