You think a tezzeret or karn scion o mf urza would be good vs the tron matchup?
I tried Tezzeret, agent of Bolas a while ago but because of the two color requirement was a bit too inconsistent for me.
Concerning Karn, Scion of Urza I am willing to give it a try. I think it might have the potential of making your very good draw even better (turn 2 Karn ), and helps with grindier matchups thanks to the card draw. On the other hand 4 cmc might be too much, I guess we'll see.
There aren't really any artifact decks where I play
Unless your meta is full of eldrazi or tron why don't you go for more Etched champion main?
About Damping Sphere I don't know. On one side I don't like to play artifact sideboard cards, but on the other it's less narrow than some enchantments.