It depends if yours are hardy to your climate or not. If you have hardy fuchsias, planting them in the ground a couple of inches below the soil level of the pot will help protect the rootball. Apply mulch as well. Check out the NW Fuchsia Society page under "Hardy Fuchsia List". http://www.nwfuchsiasociety.com/hardies/hardyfuchsias.htm

I haven't tried what you intend to do, though it sounds interesting. I have a few tenders (zone 9) planted that I plan to overwinter, as an experiment, by using the technique shown in the link below. I'll see how well it works.

I used to live in zone 6, and although my hardies died down in winter, they did return in May and fill out. I didn't mulch, but they survived. If I had protected them better, I'm sure they would have come back sooner.

Here is a link that might be useful: Banana Tree Overwintering