Hehehe, well Llama, ironically the Ettin, Cyclops, and Treant were all on my tentative list.
I may just start collecting notes for now, and when your mod comes out, perhaps you would consent to it being added to my "big game balancing package" mod? I would add some other summons as well, but if nothing else, the inclusion of your work would make the full mod that much more likely to come to fruition.
Also, some of those, like the Firebird perhaps don't have many slots? I had intended to look for somewhat humanoid forms for most (and I thought that was the best nerf for Air summons - to give them less slots), so that they would be truly thuggable (options for reinvig, resistance items, etc).
Oh and as far as the Ether Lord goes, I am intending to somewhat balance these summons relative to A) Bane Lord, 12 gems, and B) Elemental Royalty, 50 gems. The Ether Lord is just not very cost effective for 90 gems. I've completed over a dozen MP games, and almost every single game I have seen Bane Lords AND Royalty, not once have I seen an Ether Lord used.
And anyway, reiterating Llama's comment - I don't think there can be too many viable summons. If I were -only- adding summons to Astral, then it would be a stupid mod, but if every other path is getting useful stuff too, I hardly see how including Astral is an issue. The goal of my mod will not be to balance the relative usefulness of the paths, just to insure that you are not hamstrung completely by your path selection (or gem income! sometimes you get TONS of one type of gem, and nothing to spend them on - not for long now).