The AT OP IMHO, would be a definite no because as corey would say "This is not needed and only seems to be added for the sake of adding units. Also because we already have other,much better units that perform nearly the same role."
But its a decent idea (because i dont want to say its a bad one), could be a cheaper, much slower..... much less useful juggernaut.
The AT XT, ohh.... I remember this one from that one old SW game by Pandemic, those were the days. A better AT PT perhaps? seeing that it in the game had Conc. grenades and that shield ability thingy. But I dont think this would work because iirc ,they didnt reach mass production lore wise to have the numbers to still be effective 20 some odd years after the clone wars.
Sorry to crush your ideas bro but good thoughts nonetheless.