>Does anyone have any ideas for base mechanics? Roll and keep, successes, etc?
Honestly don't see anything wrong with basic d20 mechanics found in D&D or Pathfinder: ability scores, classes, ect. Just needs an entirely new set of classes, weapons, and equipment. Race could be thrown out entirely, or consist of just human and android/replicant/whatever you call an intelligent robot.
Hacker shouldn't be a class, but a skill, and one with realistic limitations. No quick-hacking robots mid-fight.
Add a system for bionic augmentations: getting them put in, what they can do, drawbacks, and how much they cost.
>And the base setting, do we want one mega Corp, three, or several?
Honestly never liked the idea of mega corps that much, though there is basis for that in reality it seems kind of oversimplified. If the real world is any implication the politics of the future are going to be dictated by governments, corporations, and criminal organizations from all over the world.
In other words, several mega corps with governments and mafias/cartels/yakuzas still playing significant roles.
>What kind of tech?
I'm a fan of near-future tech. Firearms still rule the day and most of the stuff available today is still in use, but newer models are introduced and the first clumsy laser weapons are just starting to hit the market. Energy weapons are big, expensive, and heavy though, usually mounted on vehicles that can support the power consumption. Coilguns are in a similar situation.
Bionic prosthesis are now commonly available and in the higher-end models actually better than organic limbs.
Robotics should basically be the shit you see in videos from Boston Dynamics, but refined to the point of it being very useful and commonly used. No mechas, but robots of some sort are used in construction, manufacturing, service industry, military, and private security applications. Pic related.