I keep most of my tropical flowering plants under grow-lights in the winter, as our windowsills don't get enough light to support them. And some of them will bloom under those conditions--especially the impatiens, fuchsias and tropical hibiscuses. (They will also drop leaves, as you mentioned, to adapt to the lower light levels.)

I've been limiting the amount of light they get in the winter, though, to twelve hours per day, as plants always seem to know what time of year it is. (Besides, some of the winter bloomers require the shorter days to do their thing.)

I also cut the plants back pretty severely when I first bring them in, so they will fit under the shoplight type of grow-lights which I use. And I cut them back as needed during the winter to keep them from outgrowing those lights. Most plants do survive this treatment, though some will get a bit sulky around midwinter. But, then again, who doesn't?