I think one horse could pull it, under the right circumstances. The horse would need to be pretty 'solidly' built and know how to pull. The two bay mares that are pulling it in the photo are 33.5 and 33.75 and built fairly stoutly. But, usually only one of them was doing any of the pulling; the one on the driver's left. You can see in the photo that the tugs are loose for the horse on the right. So, mostly this has been pulled by just the one horse, and she is the smaller of the two.
Terrain and distance would also make a difference. If the ground was paved and level, then it is easy to keep rolling once it is moving. It took both horses to pull it up the hills and across really rough railroad tracks. It does have the hydraulic brakes, so stopping it is not a problem, even with one horse.
I have a set of shafts for a single horse that belong to a white doctors buggy that I have. I haven't tried them on the Victoria, but I could see if they fit. The only thing is that the pin-striping on the Victoria is deep red and the pin-stripe on the buggy is gold. You might have to put some stick on red pin-stripe over the gold if you wanted them to match a little better. Or, if the Victoria was decorated and you decorated the shafts heavily, the difference in color probably wouldn't be noticed.
I need to update my website, the number listed is for my computer and doesn't have a phone attached. You can try reaching me on my cell: 580-695-7024, but I am pretty hit and miss on that and the messages don't always show up in a timely manner, so if I don't answer leave a message, but also try back if you don't hear from me.