+1 on the FlowAlongPolysrf command!
I think an intuitive implementation would be a little dialog box that pops up with FlowAlongSrf.
Just like how the Alias tool handles it, if a polysrf is selected, this command could default to similar functionality which is already done by Pascal’s FlowAlongMultipleSrfs script.
In this scenario, there would also be a checkbox with “Apply per surface” where when checked, it would treat the polysrf like Pascal’s script, and when unchecked, it would treat the polysrf like a single surface (assuming it’s a 4 sided polysrf. I can see how edge cases would be difficult).
The flip and rotate options similar to Alias would be useful too.
However, FlowAlongPolySrf (which would be the same as the FlowAlongSrf with the ‘Apply per surface’ un-checked) could also exist as a separate command if anyone needs to use it in a macro.