No more schematic chart mandating how many of what level schematic a tinker can use, it will be up to the GM whether the character has access to the design to create it. To use a device just roll a d20 and subtract level of the device, looking to roll above 10. You get to add your intelligence bonus to the roll. A failed roll means it works but needs repaired before being used again, costing 5 gp per level of the design. A one on a failed roll means it does not even go off and you still have to repair it before you can use it again. So far I have given a quick description of how each device might work, usually key wound. I f you have an idea how you would like it to work, run it past your GM. Happy holidays and happy gaming!
PS. I adapted this from the Owl Hoot Trail rpg's gadgeteer class.