96'er conversions typically and a 29"/700c to the front of a 26" wheeled frame, but if you have a working rear brake and the bb is high enough I don't see any reason you can't do it this way.

Is there clearance for a 622x45?

If the reason for the 700c to 26" conversion is availability of parts you may want to go ahead and change the front with the back. When a wheel size is in short supply, in my experience, you end up with more trouble finding tires and tubes and end up paying more for them. I would at least check if a suitable fork is available, what the cost of the fork would be, and what the difference in costs for the tires would be.

Also don't forget that these changes will effect the geometry. If the front tire is replaced with a taller tire (I don't know what it came with, so I'm just guessing on this) and the rear is lowered you'll have more slack seat tube and head tube angles. This will probably mean a more upright riding position and more sluggish steering.
If you were converting a "road" bike to an urban city bike that would probably be a good thing, but if the frame has clearance for a 622x45 tire and a high enough bb to accommodate the change to 26" I'm guessing it's not a typical road bike. Is it a CX frame? A 29'er?

Using a taller 26" fork with less rake would still change the tube angles, but the difference in rake would help keep the steering from being to sluggish. It would also keep you from carrying two different size tubes, and if you'll be posted there long enough to need a second set of tires it would simplify matters there.

If the 700c in front works for you I don't see anything inherently wrong with that, I'm just trying to give food for thought.