If it had a slight ranged deployable placement range (of say 10-20 units), it would require less endurance on bariks behalf for optimal placement around terrain and off of a high ground onto a lower platform within range..
As long as the range is not too far, that small placement flexibility buff in itself would be choice in giving a bit more extension into enemy ground potential from a standstill.
As for design overhauls.
Turret is pretty core to the theme of the kit.
Provides a body block vs non foe piercing brawler attacks as a subtle hint to the power of a smaller character size.
Its firepower mechanics are lacking somewhat due to design. Not to say it does not do the job of creating CQC damage pressure... It just could be better in design to have more influence.
I would opt for a channelled beam turret, laser targets nearest foe then arcs to the nearest foe nearby, chaining across the whole enemy team if they are too close (say 20 units), dealing less damage the further it chains. This turret design would do better to split foes apart to avoid chaining damage to each other, yet hindering their ability to form up close to each other for defence.
So not only is your team protected behind a shield, foes entering that shield will could cause a potential team wide multi foe CQC backlash dependant on how many foes want to stick around that shield.
Or a gatling gun with extreme falloff or inaccuracy at max range to provide more range and offence rather then only in tight spaces, limited to the shield area. However barrier and sentry combos are a pain to deal with and the current barrier strength would see it too strong to deal with without some duration or value drawbacks..
Without turret, it could just be a static Bubble Barrier and Damage Over Time field, but without the turret, I can't really see barik the same way.
I like THUNDERDOME's in general...
But it should be another characters ult.
As for soft vs hard CC on ult.
Any Hard CC stun or silence would provide an at the ready ability counter against channelled defence abilities and would afford barik much counterplay to a character in a defence state.
I would rather opt for a weak 40% Slow Zone, Damage over time and Mid strength Bubble Shield. A good ult for a front line class as it has all elements of defence, offence and control without any extremes, allowing it to be deployed at range without any instant combat overwhelm influence potential. I wish we had more elegant defensive ult design, front lines have mostly gone for direct combat influence ults, whereas environmental defence and offence have impact if they are designed right.
I'm not the biggest fan of simple direct influence ability counterplay, if done poorly the game thrives on clutch ability outplay options rather then performance skill.
If not balanced overall, ability outplay can create too strong dive and shut down moves.
I am surprised we have not seen another double barrier set up on a tank tbh.