Splitting up high poly objects in Maya

I frequently need to split up high poly objects with fairly messy geometry into pieces to pop on the router. I haven't really found a good workflow for this. Mayas Boolean system is pretty flaky at the best of times and the messy geo makes them even less likely to function, so I'm kind of relegated to either using the mirror cut tool for straight edges and cutting edges by hand then extracting which is an enormous pain in the proverbial.

I've poked about for scripts that'll allow for spline based cutting or the like but haven't found anything ideal.

This is another one of those things that probably has a really simple solution, but I'm wasting a lot of paid time here messing about without making any actual headway.