I read your series today and I really liked them. Your opinions are well supported, and your analysis covers each keyword from many different aspects in a broad view.
I have one correction to make though. Suspend wasn't the first ability to use the exile zone in a way that no other card could, imprint in Mirrodin block did it first (albeit in an unexciting and not very memorable way). This mechanic still has quite a lot of untapped design space.
I don't have an idea what the first keyword would be. Trample is one of the most beloved mechanics of all time, that plays well and has history. However, it's not very innovative - many attacking/blocking mechanic have been made alongside it from the very beginning, and it's not as resonant as flying.
OTOH I definitely know what will make the worst ten keywords of all time: Shroud!
Ob > Liliana
Wall > Druid except for the combo like others said
Behold >= Illumination > Pull
Agreed
Elspeth was far better for us. She is good after a mass removal or when your draw was low on creatures. Non-aggro/token decks are also interested in her, as she is quite good on defense and can grind value in a long game.
We play Nekrataal over Skinrender, Nekrataal kills more high-priority targets and can be played on an empty board. Overall they are close though.
Almost all removal that kills 4 toughness creatures also kills 5 toughness creatures. If your opponent has a sorcery speed removal for your dragon, Glorybringer is a 2-for-1 in your favor most of the time when Thundermaw isn't. Glorybringer is quite effective at killing planeswalkers, as it clears its own way.
Agreed, but I dislike five drops in aggro anyway. Their performance in this deck theater is not central to their evaluation.
Urza is better than all the Tezzerets. We only play Artifice Master, as it is the most playable of the three outside of a dedicated artifacts deck.
Beast is at least a league above ambusher.
I think Goldspan is worse than Glorybringer too, however.
Krasis >> Nissa
Scavenger > Carver > Engineer