For the purpose of this suggestion, tick means a physics update. The idea is an option (even if console only) that sets how many frames happen before a tick, with the default being 1 (every tick). By increasing this, you could make slow motion without reduced frame rate. This would be kind of like an automated F button, and should not be too difficult to implement.
This is very similar to just changing how many frames happen per second, which can be done by typing
tpt.setfpscap( frames per second you want ) in the console.