I agree with most of your analysis except for a few points.
Legacy:
Necropotence WTF??? surely it's not hard to imagine how much more degenerate necropotence is compared to Ad nauseam. it would totally warp the format. Of course necro has very real draw backs and is very skill intensive, but that does not mean it's not completely busted. and it would be pretty consistent too. Land ritual necro> turn 2 kill; infernal tutor, resp crack led tutor up necro ftw... and so forth, i'm sure there are a ton of permutations that let you cast necro turn one or turn two. The fact that it is way more efficient than ad nauseam and doesn't dis-synergies with other copies of itself make it miles ahead.
Did you read what he said in the article? I'm willing to believe him when he says he tested it and it was fine, seeing as UR Delver is the deck to beat in the format(Incidentally, that is also the reason Storm decks are cutting Ad Nauseum now). If you can make a list that proves necro is too good for Legacy I'll take it, but so far nothing suggests it's overpowered, as it has never been seen in the context of Modern Legacy.
Except that Ad nauseam and necropotence are very different, kinda like the difference between Time reversal and timetwister.
I don't know enough about legacy to claim I can make an optimal necropotence list for that format. But why is the burden on me to proove that necro is degenerate? It should be up to the people who claim it's safe to unban to proove their point.
Granted the card pool is totally different from the day of necro's reign, but the last time it was legal the win con was nothing close to tendrils of agony.
Life loss is extremely relevant in today's magic of course but that only really applies to necropotences cast after turn 2. It's also easy to somewhat mitigate that by running 2/3 copies of tendrils of agony and going for mini tendrils in between Necro activations.
I won't claim I understand every subtlety and interactions of Necropotence because the card is extremely skill intensive and has complicated mechanics, but the raw power of that card is insane.
Black source>ritual>necro is one of the most powerful plays you can make in vintage, the only reason it's not that good is because it involves a restricted card(=inconsistent) and mental misstep can turn that necropotence in your hand into a very dead card.
But here we are talking about unleashing 4 necropotences in a format without mental misstep and correct me if I'm wrong but I think vintage can still punish you more than legacy for passing the turn after resolving and activating Necropotence in the first two turns.
I am usually very wide open in terms of unbans and unrestrictions, but Necropotence is one of the most powerful cards ever printed. There are so many cards that are safer to unban in legacy, so why take that big of a risk?
Vintage:
Brainstorm is just too good and doesn't do anything to increase diversity, it's main effect is to make anything blue much better without distinction.
So? Something like 98% of non-shop players play blue decks in Vintage; I don't see how that changes anything about color diversity(Not that i think Color diversity matters).
So it's an unrestriction that doesn't help, and the whole idea in the article was providing a tool to balance the power of treasure cruise for decks that can't abuse it as well as delver. Thirst for knowledge is a much better candidate to help decks like bomberman be competitive again.
it doesn't help in any way to mitigate the effect of treasure cruise, if anything it makes cruise even better.
That's funny, because the last speculative argument against unrestricted brainstorm was that it would make Oath and Vault Key combo too good. Brainstorm doesn't change those decks' matchups, because everyone gets to run brainstorm. The people who don't(Shop Players) will not have unwinnable matchups because of Brainstorm. Gush Storm and Delver can't suddenly fight through a constant rain of spheres because they have brainstorm.
Well brainstorm will be slightly better for certain decks than others, but it probably won't make decks that have been pushed out of the metagame by Delver cruise competitive enough to make a comeback. It will also make current top tier strategies like Delver and oath stronger.
