Atlas in Paladins is what a tanky Symmetra could have been.
They have a similar short ranged primary and charged secondary fire.
Atlas’ barrier is Symmetra’s but reduced to a rectangle instead of an infinite plane. There’s a customization for it that acts like a speed boost if you walk through it, which Sym could have on her version.
Tank Sym could have Atlas’ defensive ability, which is basically a Recall that takes 4 seconds to use. Call it “reconstruction” and explain it as restoring a saved state using hard light repair or something.
Tank Sym could also have his ultimate, which turns his weapon into a device that fires three projectiles which can imprison enemies. It would be like an Earthshatter, but single target and neither enemies nor allies can target you while you’re affected.