The truck can cap, so there's a decent argument for building the truck first and letting it Kubel around for a bit until you've got 45 munitions. It'll cap faster than a Rifleman squad because it moves between points faster.
The Stuart as is feels like it has the anti-infantry performance of the AEC and the anti-armor performance of the T-70. It's meant to be a debuffer to support Shermans, but its abilities just aren't up to that at the moment.
Making its abilities not share a cooldown might help. That, or Flanking Speed/Ninja Smoke so it can actually pull off its snare without dying.
They shouldn't have put this ability back in Overwatch at all. The balance team was on the right track when they started removing things to make way for new stuff.
Then they reversed path entirely and put everything they'd taken out back on top of the new stuff.
They should have stuck to their guns and held these abilities back for the new commanders. This game does NOT need more 'do everything' doctrines: Overwatch should be split across two commanders.