You can grow them as you say >> and some roots will grow into the earth, but you will still need to root prune eventually in the bucket as eventually it will get rootbound , some types grow more aggressive.
For this you might as well put the plant inground and not have to do rootwork (pruning roots) nor change soil and keep the above ground part of plant trimmed like one would normally do in a bucket or
large container etc.
The amount of space used then would be about the same above ground.

Best Health
Martin

I grow my fig trees in large containers with holes on the lower side of the container. Then I plant the containers in the garden. I was forced to do that because I live in cold climate. I pulled the containers and took them inside the Garage. When I digged the containers there were a lots of roots travelling from the container holes to the Garden soil. I feel there are not much roots accumulating in the container. I gave them about 50 holes to travel through. Every year I am cutting the extension of roots out isn't that trimming enough. If I leave the trees out they will freeze and die. I try not to put much soil into the container. When I give them fertilizer I make a tunnel around the container and put the fertilizer not into the container. One My of my trees The (Italian) did very well and produced lots of figs. The others are very young to produce last year I expect production this year I hope. My Banana trees are doing very well following this method of containers planting in the soil.

I dont grow like this but its a good way yes for various reasons yes.
My neighbor has his Sals + VDB in 20 g containers and lets his roots grow inground and yes the roots in the container need pruning as ive done it for him and they grow like the ones in my container above ground on a cement patio, the roots will fill the container and i have pictures of it when i did mine that i posted in past his looked similar. After 3 seasons it needed it . Sure you can delay the process but the overall health of the tree will start to decline as there will be way to many roots competing with one another.
Want to see a picture?
Martin

Oh what the heck pictures are fun. Mind you i still dug and cut away afterwards as i was not finished.
Pictured is my plant but as stated in above post neighbors looked similar.

{{gwi:844719}}
{{gwi:844720}}
{{gwi:844721}}
Martin

thanks for the info. im just going to plant it on the ground and trim it.

My space is also limited. I grow all of my fruit trees using variations of the "backyard orchard culture" method, which means keeping them compact, branching low, and purning such that I don't have to stand on a ladder to pick fruit or prune. That includes cherries, apples, peaches, plums, and a new attempt at mulberries, as well as figs. The difference for figs is that they have to be pruned in winter or spring (for fall cropping) or after fruiting (for breba cropping).

I have a Desert King that I keep as a bush, cutting long branches back, after brebas, to 1 to 2 feet tall, and leaving the longer branches alone. With new growth, it gets to about 6 feet tall and 6 or 8 feet diameter of branch length. In my area Desert King is breba only, so I don't winter prune

I have a Petite Negri that is reputed to be dwarf. I prune it back taking about half of the long branches in winter, so I get some breba. The shorter branches I leave on. Unfortunately it fruits late with the main crop and I lose some to freezing (Portland Oregon area). I try to keep it as a bowl shape, with open center for sunshine. It is 9 years old and is 7 feet tall and well branched, gets zillions of small to medium size figs.

I have a Lattarula and an Hardy Chicago that are both pruned about the same way as the Petite Negri. I really don't see that Petite Negri more naturally dwarf than Lattarula or Hardy Chicago are but they don't get much chance to grow bigger, I don't let them. The Lattarula is 7 years old and about 6 feet tall, and really came into its own last year, with a few dozen figes spaced out over several weeks (main crop) but only a handful of brebas. The Hardy Chicago has produced when the others did not, but sometimes does not produce when the others do. It is 6 years old and about 6 feet tall. I keep these to a bowl shape.

Some years I get ambitious and root prune using a shovel and dig straight down, in a circle about 2 or 3 feet from the trunk. I don't know if that helps.

Anyway, I'm no expert. Some years I get good crops and other years I don't. Different varieties give me better crops on different years. But they are all pruned to compact size.

Keeping them compact lets me have more trees. I can easily cover them with net to keep birds out. I don't get tons of fruit but usually have stretches of several figs, or several bowls of figs, for weeks on end, because I have varieties that fruit at different times.

You might also try planting 3 trees in a hole - if you google on backyard orchard culture there are illustrations. I don't know if that has ever been done with figs - you would be the pioneer. Doing so with other fruits dwarfs the trees and gives you 3 varieties in the space of one. They should have similar vigor for that practice.

I hope that's helpful to you. Good luck and happy planting.

Daniel