You can use parts! This is exactly what they’re for!
Eg: I’ll have 4 partterns of drums (with the 4th bar of the 4th pattern being a fill) then you can use part 2, which has exactly the same drums (or different as different parts can contain different samples)
As for using different projects, I don’t really see why as you have 16x16 patterns of 4 bars each which means 1024 bars per project!