Hello,
I have hand soldered through hole components to surface mount pads in the past, but this is hand soldering. I have been the leads 90 degrees from the body, then bent another 90 degrees a ways down the lead length until they were parallel with the body. This gave me a way to solder them to the top of the board and get a good solder joint with no problems.
Again though, this was hand soldering. Flow soldering would be different because the parts have to be held in place and in the case of something like resistors, they have to be held upright too. If the leads are bent slightly outward like your picture shows, they might stay upright but they are still too vulnerable to movement by the slightest vibration or even the solder itself as it passes over.
What might help is to have small holders made for each type of component. The component would be matched to it's holder and then placed on the board. The holder then disintegrates as the heat hits it, or it has to be removed in another process step.
There are plastics made for this purpose for IC sockets, but i've never actually tried any of them so i cant say for sure how well they work.
As mentioned in one of the previous posts, glue might help as long as it can stand up to the heat. The part would be simply glued down in the right position and orientation.
I have actually used glue in the past but again this was for hand soldering. I used Elmer's Glue (chuckle) because that was all that was needed for temporary hold down while i soldered a couple leads on the surface mount IC package. The glue stays wet long enough for me to position the part perfectly on the pads, then let dry, then solder. Im sure there are better glues however for automated soldering. There is a high temp silicone that would be ideal but it does take time to dry, roughly 12 hours, so that would take an additional lengthy processing step just to glue them down and wait 12 hours.