It’s a race! The fastest angel in heaven vs. a champion of the Prince of Pride.
The stakes? Well for Sandalphon to even bother, there’s probably got to be a McGuffin or a Divine Intervention of some sort involved – but the real stakes are going to be the state of Sandalphon’s soul.
It is highly unlikely that Lucifuge Rofocale could find a celestial or spirit who could best Sandalphon in a fair race – but he might be able to find someone who could at least challenge the fastest angel. From there it will simply be a matter of structuring the course so that Sandalphon needs to decide between keeping his title and doing some serious harm to the world.
Finding a champion who could challenge Sandalphon enough to force him into morally questionable positions would be an ideal job for some PC Infernals – especially ones interested in either the sciences or the Marches.
The outcome of the race could be pre-plotted to fit your campaign, or it can reflect actions taken and decisions made by the PCs. If you opt for the latter option, you should probably warn your players that their actions will inform the larger universe in ways beyond obvious in-world cause and effect.
Either way, have fun with it (and read some Flash vs. Superman comics – they may give some good ideas for descriptions you can use or challenges you can pose).