Can I nominate that, if the trader is altered, you do NOT make it harder to stack a full set on a planet? I'm not yet sure if changing P-Inhib to simply doubling damage to shields would be ok or not yet, but I do know that my games would be close to impossible to win without the Zenith Cheese Merchant. When you have four exo sources and they are all tuned to 5/10, you rather NEED a shield that can take such a spear. That 'warps to a new world every time something is bought' idea would do nothing to the AI, since they only buy when it leaves a system, and make stacking a full set practically impossible. Perhaps, as someone else suggested, give the AI a better chance to buy things. Perhaps 10%, but make it so it can only buy something every so often.
The problem I see with just letting the AI buy more stuff is threefold:
First, lots of the Trader Goodies are only good in conjunction with something else. or only good against specific targets. For example, the Planetary Armor Inhibitor negates armor and shuts down shield. But the Human player doesn't get excessive use of those - Riots, Champions, Shieldbearers, pretty much. The AI, on the other hand, takes huge advantage of them in Exowaves with Shield Guardians and Spirecraft Shieldbearers, as well as everything the human can get.
Related to this: What good is the AI with Trader Goodies on a Mk II world with 3-4 guardposts? Even enhanced, there simply isn't enough base strength there to become truly dangerous. It also leads to problem 2 -
Second problem, anything that the AI can get can become the property of the human player. If the AI builds a strongpoint with a full set of goodies? Yay! Cloaking, Warheads, and more toys for me!
Third, the AI gets so much more of everything that if it could get a full set, it could make the game basically unwinnable for the human player. Imagine this: A Tachyon Command Station Mk IV, with a BHG, 2 OMDs, Armor Inhibitor and Armor Booster, SuperFortress, all under a bunch of Mk IV Spire Shield Guardposts. Toss in a few Sniper or Implosion Guardposts, a Munitions Booster Guardpost, and a Gravity Guardpost. How do you beat that?
That's also not an absurd example. I've encountered a version of that that had 'merely' a BHG and SuperFortress.
Some things that could be done instead? Maybe make the Armor Inhibitor have a limited range. Maybe convert it to something like an Anti-Structual Ion Cannon - It gets a regular supply of shots that insta-kill shield modules. Maybe it adds "Armor Piercing 999,999" to all units in the system.
The Radar Jammers could change so that they both work the same, but with the Mk II being better than the Mk I, a 75%, 50% progression? Or maybe a 50%, 25%.
OMDs I think are good right now. They're equally bad when the AI gets them as when the Human gets them.
The Counterspy is actually one that is usually better in AI possession. It can really shut down scouting or sneaking attempts by the human player. But the human, when dealing with cloaked AI units, is usually dealing with hundreds of them. The Counterspy simply doesn't fire fast enough to make a difference there.
That said, I'd like to be able to buy the Attritioner and Warhead Interceptor from the Trader, as well. You can already capture them, so why not?