He could mean doing something at technical level, not removing the ability to exit vehicles.
I mean Lelic could just make a variable, named appliedAfterDeployment or really anything else and apply it to every buff, then set it to false in every buff that shouldn't be stackable and voila, we've got rid of every single USF vehicles stackable buff bugs and many more.
Minesweepers aren't a no-brainer upgrade. If you want your engis or pios to serve in defensive/support role, you take minesweepers. If you want offensive role, you take flamethrower or leave them be. More upgrades should have visible and important drawbacks, not less.