You never know what troops they already have in the pipeline. We also don’t know, exactly, what they consider acceptable for the Epic power level.
The one I liked most of yours was probably what they consider a legendary power level, so they probably excluded that one right off. I also really like @Rickygervais, but I wanted to see a row and column destruction too, for all 8 arms hitting the board. I like @Jainus troop as well, but dislike the green as the color seems out of place for Mech design, while giving Mechs a much needed boost, I think.
Of course I also believe the first community designed troop should be above average power level for the rarity.