There are probably solutions to the root problems.
Bonsai growers prune roots, so you just need a big double walled structure. The inner liner has many holes which is good for drainage and allows roots to grow, and you prune roots growing out of the holes.
I say 'Just' - having read this it feels very wrong and anyone who knows anything about how tree roots actually grow will be able to point out the flaws. But it can't be that hard. In West Drayton there's a garden with everything grown in pots. (http://goo.gl/maps/G2oXN)
Bonsai growers prune roots, so you just need a big double walled structure. The inner liner has many holes which is good for drainage and allows roots to grow, and you prune roots growing out of the holes.
I say 'Just' - having read this it feels very wrong and anyone who knows anything about how tree roots actually grow will be able to point out the flaws. But it can't be that hard. In West Drayton there's a garden with everything grown in pots. (http://goo.gl/maps/G2oXN)