can i mod the flak turrets option to also include them on Gauss cannons?(as well as the same concept for the other race tac structures)?
Yes, but whether or not you must modify the model of the structure first to give it weapon hardpoints (or if the game will allow you to just specify a random point on the mesh), I don't know.
can I mod that instead of tac slots and logistic slots, each structure from either tac. or log uses 1 pop from that planet(IE: if planet has a current population or 30 then 30 structures i can have around the planet)
I don't believe so. However, you can mod the number of Tactical/Logistical slots the structure uses (including 0... you might even be able to do fraction) as well as how many each planet has.
instead of using fleet supply and command points, could ships also use population numbers(like above) and i could still use the fleet logistics for different levels of ships or whatnot.
Again, for population, I don't believe so. But again, you can modify the amount of fleet supply used by the ships (but not the command points) and can modify the max available fleet supply and command points.
can i rework superpower guns to "create" random events, instead thier not random.(IE the Novalith cannon no longer shoots a Super Nuke, but instead creats a "magnetic storm" within the gravity well for like 5 minutes etc but it disapeates and doesnt move around froim system to system
I'm pretty sure this is possible.
can i make all planet exploitation lvl 1 tec, with like 10 upgrades to each one, whereby each upgrade gives a 20% population increase(a 200% increase at lvl 10) as well as give bonuses and minuses for races on certainb worlds(IE tec loalists get a 10% bonus to terran worlds and a 10% minus to volcanic worlds while the tec rebels get a 10% minus to terran worlds and a 10% bonus to volcanic worlds)
Are you talking about the researches in the civilian section that increases max population of a planet type? Yes, however, your negatives would have to be a part of those researches, too, as I don't believe you can make that a part of the default racial bonuses/penalties.