i looked into this a while ago... the canna forums seem to be the main resource for this topic.
Among the contributors to those forums, the general consensus seems to be "do a regular repot during transplant".
Personally, I agree. I use 1 gallon smart pots. I considered the nesting pot transplant idea, because I saw some roots coming out of the bottom of my smart pots. Ultimately, I decided to do a regular pot-up. There was little to no transplant shock, and the occasion gave me an opportunity to observe the roots and inoculate/fertilize them effectively.
I were you, I would take the weekend and do it. Or try to streamline your process so it only takes a day. The bowl method works pretty well.
In favor of the alternative:
I watched a video that was smart pots with coco/hydroton on an ebb & flow with roots trailing down into the grooves of the tank.
There are many ways to grow, and it comes down to trail and error experimentation. You may be able to find different ways to make this idea advantageous. For example, maybe it will make it easier for you to water them an appropriate amount after transplanting. 1L to 12L are approximately the same sizes I use.
I like skullbiker's idea of root pruning the outside of the 1L to overwinter them. I've heard of doing a similar thing for in-ground plants. Maybe it was in pepperguru's overwintering guide.
I know roots will grow through fabric pots, but I sort of don't like the idea of having a pot inside a pot.
It's like peat pots, how they sometimes have root problems and don't transition very well. Maybe if they have optimum growing condiitons with a dialed-in environment and watering/fertilization.
Also, internationalfish mentioned that it might affect the way the water and air [percolates?] through the soil. It makes sense that there would be some effect. Though, I'm sure there is no research on this. If you decide to do this, I probably wouldn't fertilize the inner pot heavily, because of the risk of over fertilization or salt buildup/nutrient lockout. If your plant is in a pot inside another larger pot, then you don't want to have to flush the soil.