As far a a waste of time and money goes, your project would be minimal money, and I'm guessing you might have some extra time, so why not?
What type of paceman? Ours only runs the light 50g balls, and they would bounce off a sheet of ply laying on grass without major issue. Heavier balls maybe not. Having a hinge would be a great idea to avoid an uneven join which you will always seem to find.
Be aware that sheets of ply generally come in 1.2 x 2.4 m, and while two of them hinged together would be portable, they would be heavy and awkward to move on your own - especially the 19mm stuff.
We run the paceman on a 12m pitch, and that makes it easier to hit a spot.