Yeah, I was thinking Swann’s Science Vessels, since they can be upgraded to not use energy to repair. And just keep a Goliath in ‘hold position’ but out of the Goliath’s attack range and within the VT’s aggro range. Again, I’m not aware of the VT’s attack/aggro range. I thought it was quite small/short distance.
Other option is a Stalker under Vorazun’s Dark Pylon (50% increased shield regen for cloaked) and potentially backed up by a Karax Shield Gen, also within the DP (400% increased energy regen for cloaked).
Vora’s Darchons and Arty’s Archons have 350 shields - but such heavily shielded units shouldn’t be needed if it needs to last un-attended. Basically, two consecutive attacks should not deplete shields, or the time between each attack should be enough to fully regen the shields. Or repair/heal for terrans.
Edit: Or a Kerrigan Ultralisk (melee) on hold position being healed by Nikara farther away, also on hold position. With Nikara having the double heal-rate upgrade.
Or Blaze with Nikara. I’m sure even if the VT’s attack/aggro range is short, it’s more than Blaze’s and with his ultimate upgrade of just 30 dmg taken per attack, Nikara can heal it before the next one, probably even with un-upgraded heal.