What you need to evaluate is whether replacing the suction and delivery piping above ground is worth it.

It's odds on that your suction piping from skimmers and drain are already 1.5", so increasing that is debatable. The delivery piping might be changed, but again you have to judge whether the changing this will will improve the flow dramatically. Any increase in flow will be seen at the suction side with possibly some cavitation. That is the main tradeoff.

Don't forget too, that the return jet nozzles will still be the same size, so that the restrictions will be there as well. You can increase the jet nozzle sizes, to reduce that restriction, but then the suction side will really start showing signs of cavitation.

I would say that if you have adequate flow with the existing setup, leave it alone. i.e. If it ain't broke, don't fix it.

Hope this helps.

Pat