On Economy
Economy changes primarily affect how the game feels to play. Going too high makes your only limiting factor build time of units which makes economy totally irrelevant, but beyond that, I think we want an economy strong enough that waiting is reduced. There is probably no reason for refleeting to take more than 5 minutes with no Harvester upgrades. That's ignoring static defenses and starships, so just fleet ships.
However, I think static defenses should probably have a m+c increase. Slow fleet rebuilds prevent the game from advancing and eat time. Slow defensive rebuilds can be covered by a fleet (although obviously weaker) but also, if you know the AI can't counter-attack, you can carry out offensive actions during a static defense rebuild.
On Data Center
Raiding these is an intersting part of the game. I'd hate to see them go away. I wouldn't mind them getting harder to raid though. Preferrably through interesting defenses rather than just x10 health.
As for how they enable low AIP game play, I think this might be fixed by changing something else to ignore negative AIP. Right now the AI gets unlocks based on AIP gained, and ignores negative AIP. What if CPAs ignored negative AIP? You might be at floor, but those CPAs are still going to hurt.