That would probably require a transition from the "infinite resource" or "constant resource" model that has been fairly standard, but it's not necessarily a bad thing to move away from that. For instance, you could have VRCs generate happiness units in some form of commodity and transfer them throughout your empire. This would be particularly useful if you had some kind of morale percentage boost improvement, as opposed to the normal +x ones we have now (basically a research coordination center, but for morale, although I'm not sure what the logic behind it might be).
This is how I understand the trade and/or food system may change within Elemental and thereby GC3, and there are certainly other things that can be moved to such a system as well. The downside from a gameplay perspective, such that it isn't an overpowering mechanism, is that of course things take time to be moved from planet to planet. So you could theoretically send x production (in terms of workers perhaps-although this may be too close to the failed employment aspect of GC2) from planet A to planet B, but it might not get there in time for the ship that you need built to be built any faster, etc.
But there may be things that wouldn't benefit from such a system as well.
I completely agree on the tech whoring aspect-apart from the limitation introduced in DA whereby you can only speak to the AIs once per 8 turns (4 if you're super diplomat), which I've heard there is a loophole in but have never managed to find it, I would think one transaction, regardless of how many items are involved in it, per x amount of turns would be an ideal limit. Maybe even have a limit on the value of the items tradeable based on how close you are to the other party-although this could be, as stated previously, on multiple metrics, in the vein of likes/fears/trusts/etc.