Well... I think it would be possible to reach a consensus. For my part, I love the picture you posted, but at the same time, I would like some additions or adjustments. I would like the mountains to be a bit less high - and let me be as clear as I can: I do not want them to be hills, I want mountains. Just lower. And sure, the mountainside where Sirion springs forth from the rock can absolutely be steep, as in your picture, I have no problems with that. And I don't want the fortress on the cliffside to be the only part of Barad Eithel. If the idea is to be a part of the siege and the idea is to hinder attacks from Angband on Beleriand, the Noldor would want to be able to get out on the Ard-galen swiftly and at short notice. That will not be possible if they are high up on the mountain. I suggest a system of tunnels and stairs inside the mountain connecting the upper fortress and a lower one that is situated with its back to the mountain, where initially one wall encircles an area with barracks and workshops. The lower fortress should be placed somewhat to the south of the upper one if the elves want to use the river as a part of a defence, or north of the river if they want a more offensive position and a quicker access to the Ard-galen. Horses roam the adjacent area but at some point another wall could be built some distance from the fortress, probably with gates and a bridge crossing Sirion (place of this depending on whether the fortress is north or south of the river; I looked for a map or layout that showed the place up close to see if there was evidence of the exact location, but it's probably exactly at the spring itself, or very close). They will have horns and other means of communication between the upper and lower fortress.
Thoughts?