I don't think the Eye of the World was a well at all. It was specifically described as a pool of untainted saidin created using BOTH saidin and saidar. I think saidar itself was used as the vessel to hold saidin, thereby sacrificing the need for a physical well. Judging by the amount of Power channeled by both Aginor and Rand (enough to de-age Aginor, destroy horde of Trollocs and repel Ba'alzamon), the Eye's capacity as a well would've been insufficient. Size, in the case of wells, do matter. And the Eye of the World would've had to be the size of a big lake to contain that much Power as a well.

While I do see the similarites between a well ter'angreal and the Eye of the World, there's a big difference in structure if not function. Like how saidar was used to funnel/filter saidin, so was saidar used to contain a pure sample of saidin.

As for your point about channeling through a well to touch the DO, that is ingenious but again, size is the limiting factor.