Looks good. Amazing ingenuity.

Can you modify it so that it only releases a gumball with an Extra Ball or Free Play match? And operate on other machines?

Would it be difficult to alter the hopper so that it could dispense other novelty items? Like Pokemon cards. (I'm thinking of my 8 year old nephew here and ways in which we can get future generations playing pinball instead of Skilltesters.)  

Can you modify it so that it only releases a gumball with an Extra Ball or Free Play match? And operate on other machines?  yes :) for any pinball machine the gum ball hopper dispanse when you have match or extra ball

Would it be difficult to alter the hopper so that it could dispense other novelty items? Like Pokemon cards. (I'm thinking of my 8 year old nephew here and ways in which we can get future generations playing pinball instead of Skilltesters.)
yes :) this is kit 4

thank you!