This would be a concern to me. The cost of getting that sorted now regardless of what it actually is would outweigh the drama of a toasted head or a breakdown down the track.
A preventative waterpump swap isn't a bad or unnecessary bit of maintenance. I've read that the plastic impeller can fracture and be held and function by the angle of the fracture itself. I did mine recently on a different BMW engine, that scenario is practically what happened to mine though mine let go in a short space of time.
The replacement I installed had a cast metal impeller, Seems a bit more trustworthy.
Regardless of where the coolant leak is, you shouldn't have one.