Perhaps I've gotten lucky in not moving the enlarger head, but I do know that you don't have to open the door to the condensor lenses completely to swap out the filter. The door opens smoothly enough for most of its swing; it's only in the last bit of travel that the door really throws itself open (at least on my D2V), so if I hold the door open with one hand without opening it all of the way, swap the filters, and close the door lightly, I avoid the double-image issue. In fact, that's how I've done it since I got my D2V (something told me that the "ka-thunk" that happens in the last bit of travel for the door would be problematic, so I just avoided opening the door fully from day one), and I've never had a double image problem.
Making a set of under-the-lens filters shouldn't be too difficult if you want to go that way. Someone, somewhere (don't you just hate sentences that start that way) did a series of experiments that showed that there was no measurable image degradation with filters that were used under the lens as long as the filters were in good shape. There are filter holders made for the Omega enlargers specifically to hold filters under the lens, and as Donald points out, making a set of under-the-lens filter should be reasonably inexpensive.
But play with the door on your condensor head a bit and see if yours works the way mine does. If so, then a light touch will allow you to swap out the filters without too much worry, as long as you don't let the door swing fully open on its own. This has been my chosen way of working with the D2V, and I've yet to have a problem with swapping out filters causing a shift in the image on the paper.
Best of luck Neal...the D2V really is an amazingly long-lived peice of equipment capable of amazing results.