right now i'm focusing to integrate the paintball mecanism in it but i plan on adding LEDs and sound probably controlled by an Arduino.

That's not what I meant, a lot of paintball markers are run off of an electropnuematic solenoid and a board with the trigger activating a microswitch. This gives a higher rate of fire and a much lighter trigger pull. Google "ego sl74 ramping" and look at the how much it spits out, more like pocket infinity than a single shot mechanical gun.

Ahah sorry, yea i know what an electronic marker is, i just misunderstood your question. right now, i just drew the slot for the trigger mecanism. just to keep things simple and test things first. but i'ts no hard at all to incorporate the electronic system in it or the response trigger. would be nice if the final product could fire burst rounds, it would feel more like a pocket infinity :)

Id recommend maybe using autococker parts cause you can customise the shit out of them and there are plenty of parts, but they have to have a moving part to open the valve, are you planning on completely designing everything?

Coming from someone who has owned many cockers over the years, I'd recommend against this. They are inherently more complicated and without a lot of patience/experience/both can be a real pain to work on. I'd actually recommend something in the magfed segment. A lot of people build custom guns by starting with a Kingman Hammer 7 or Tippmann TiPX. In this case the TiPX would probably be the better route as it is not pump action. Or maybe break down a Milsig M17 and use it with a custom box mag? The M17 has mechanical full-auto and with some sort of box mag you'd definitely get that Pocket Infinity feel