Updated: I got it done. Pictures linked for clarity.

I removed the screws holding the brush bristles on my pool brush, and connected a flexible rubber feed pan (picture in post above) to the metal frame with about 6 inches of wire in two places so small movements of the pole wouldn't lift the pan off the bottom. I placed the feed pan over the main drain. I cut the drain line and put a test plug

in the end. I used a PVC Compression Repair Coupling like this



to do the actual connection. The repair coupling slid over the test plug, so I was able to connect the pool side of the repair coupling before I removed the test plug, as well as slide the rubber seal and coupler nut onto the new pump line. With the coupling in place, I unscrewed the wing nut on the test plug with needle nose pliers, and the water in the line pushed it out of the fitting. I slid the new line to the pump into the coupler, and tightened the pump side nut. I didn't even drain a gallon of water into the pit while doing it.

I didn't make the final PVC joints above ground until after the connection to let me have maximum flexibility to move the pipe around, so I didn't turn the drain valve on until this morning. All good.

I learned that the water/antifreeze mix in that drain line stinks. All the more reason to start the pump with the filter set to waste when you open.