i like the idea, if they decide to stick with the whole champion elemination mode then they should expand it. there is so much room to go deeper here.

what i like about your idea is that players cannot use the same 3 champs all the time. another way to achieve this would be banning champs 1 or 2 champs before picking.

by the way, do we know how many champions there will be at release? i remember hearing that there are a lot more planned

in duel mode I think the champion picks should be blind, they did this in the later version of street fighter games to stop people counter picking online, its very hard to design a game which accounts for all variables and I am already seeing some evidence of counter picking, which its disadvantageous to some players as it offer some people two picks in a row before the other, so something needs to happen there.

Preferably increase amount of champs in duel to 4 or 5 too if the insist on this format.

yeah, i'd love to see player build their own Duel champion team

The champion amount should be increased anyway, but there is nothing wrong with counter picking. Even if someone has two picks in a row, then the player picking twice in a row is being counter picked, its outweighted by the fact the player who picks twice has influence on the picks of his opponents (some players even now just play what they are good with, minding more what map is played rather than what picks the opponent has, Cypher said that in his interview and that's something to take advantage of) there's mind games and strategy possible. None of the players have an objective, disdinct disadvantage, nor advantage because Quake Champions don't have hard counters, with an exception of Nyx/Visor abilities, but those are just abilities and you can't counter anything else as the balance of other atributes between champions are determined largely by the playstyle and skill of players, considering the values themselves are within a reasonable degree of accuracy for balance itself.