If the "shopping cart" option honestly was the best way to help them, sure it would.
Granted, the best way to fix the problem is to make the AI less unreasonable to begin with, but that wasn't exactly an option in IV. Hopefully in V they've accomplished that to some degree. However, we do know that the AI will still be making demands about how we run our empires. The way we're hoping for this to be done reasonably is to give the player the power that the AI has. If they can say "stop expanding," we need to be able to say it, otherwise they can shackle us then do as they please with no consequence. If they can say "keep your troops away from our border," we again should be able to say the same, so they can't expel our troops and then launch an attack themselves now that we're out of position. That sort of stuff. Redlining is just another potential thing that may help us have more equal footing.
No, redlining is not a power the AI has. I have explained this again and again. It is just a shortcut for the convenience of the human player. Redlining is effectively just rejecting a demand under all circumstances. The human player can essentially already do this; if, for example, you just decide for yourself that you are going to reject any demand about giving up your iron, just reject all deals involving it personally.
The only difference between redlining and what the human player can do is the fact that the rejection is preemptive. For most deals, this makes no difference, because most deals carry no penalty if they are rejected. Demands are the exception, as rejecting a demand causes a relationship penalty for the human player. Thus, preemptively preventing a deal could be useful for the human player. But just because something is useful is not a good reason for the human player to be capable of it. It would be useful for the human if they could reject all wars preemptively, but that would not lead to good gameplay. If, however, the AI got some kind of advantage from redlining that the human player didn't have, that would be unfair and people would be right for complaining about it.
But does the AI get some advantage from being able to preemptively reject demands? No it does not, at least not as far as the human player is concerned. The reason is because AI demands and human demands are actually very different. The AI has a relationship score that to some extent controls it's actions; the human does not. When the AI makes a demand of the human player, rejecting it affects the AI's relationship score towards that player. However, when the situation is reversed, there is no relationship score for the human player to be affected. Thus, whether or not the AI rejects the deal, it suffers no in-game penalty from this. No relationship score is affected. Thus the AI has no reason to prevent itself from receiving demands. It receives no penalty from rejecting demands. In fact, the only reason it ever agrees to demands lies outside of the game mechanics entirely and has to do with the player's emotions, but even then redlining offers no advantage because the human could become angered at a resource being redlined just as easily as it could at a demand being rejected. So the AI gains no benefit from preventing demands being made of it; in fact, it would have every incentive to just let you keeping making demands and ruining your relationship with it, because you would only be hurting yourself. If redlining gives an advantage to anyone, it is the human player, because it prevents him from making demands that would be automatically rejected, and thus from ruining his diplomatic relations with no possibility of gain.
The only way redlining could possibly offer the AI an advantage is in preventing it from receiving demands from other AI's. If redlining actually does let it avoid diplomatic penalties here, that would be unfair, and would represent a design flaw. However, the solution would not be to let the human player redline, it would be to make the AI suffer those penalties regardless of whether it redlined or not.
Again, redlining gives the AI player
no advantage, at least as far as negotiations between humans and AI's are concerned. To give the human player redlining is to give to the human an advantage that the AI doesn't have. There is no reason for this; it would just make things more complicated without improving gameplay at all. Again,
Redlining is not an advantage for the AI. It is a convenience for the human player. That is all it does.