Containers and Rootstock

I'm interested in growing fruit trees in containers, mostly apples but any fruit tree that can handle my climate. I live in the southern Rocky Mountains, zone 5b at 7000 ft. We have cold winters, hot summers, sand alkali soils and wild temperature swings (today is 77 and sunny, tonight will be 38, 1st snow is forecast 2 days out).  I have read over and over that fruit trees in containers should be on dwarfing rootstock. I've also read that the trees will need permanent support and protected through the winter.  Ideally I would like to leave these containers in one spot forever. The option to put them in the ground someday is another desire. That has me thinking a hardier rootstock might be needed.

Would using a hardier, non dwarfing rootstock eliminate some/none/all of this issue? I know that most bonsai trees are grown on their own roots, so it seems odd that fruit trees need dwarfing stock. Wouldn't the small container (and pruning) dwarf the trees regardless of rootstock? Or is it an issue with roots shattering pots or taking a long time to fruit?

I will be using either M111 or B118 for inground planting of apples. Has anyone ever put these in a container?

Welcome to Permies, I have three year old Honey Crisp on M111 in ground in the high cascades roughly same wild temp swings, first year to fruit was this year so no real idea of how well they will do in the future. Next season I'm going to try Malus Antonovka root stock for in ground and even though full size, with lateral pruning and training I'll try to keep the size down.  

I know the 111 and 118 will do well in the ground here, I'm just not sure how they would handle containers.

The bigger rootstock trees may survive, but will not do well in a pot.  Better off getting the M29 or Bud5 rootstock and trying to get them in a 10 gal or larger pot.

If it's M111, just plant them in the ground - find a way!

I've found some more info since posting this.

1) I've learned that container trees need to be hardy to one zone colder than your actual zone to account for the roots being above ground. Some sites say 1 zone with insulation, 2 zones without. I'm in 5, so I suspect that anything common in zone 4 will be ok with a little protection.

2) I found a website that says using standard rootstocks is becoming more common in containers and that the containers do the dwarfing.

3) 2 users on another forum confirmed that their container trees on m111 and b118 are doing better than those on dwarfing rootstocks ... and that M27 (arguably the most recommended) is doing the worst.

4) A grower in the Yukon (zone 1) posted that he uses standard rootstocks, grows in bottomless containers, removes all in ground roots every fall to bring the containers into shelter. He says that all dwarfing stock has failed when doing this.