Armor, a machinegun, or an AMS.
If the design benefits from CASE and is for an era where it's available it should already have CASE before I'm calling half tons extra. If the role calls for a recon camera, same. Searchlights are quirk quality and not normally worth a half ton. Light TAG is SLDF deserter kit and I very rarely deign to design for those factions.
But if I'm already carrying machinegun or AMS ammo sticking a second (or third or whatever) machinegun or AMS on another facing may be better than 8 or 9 points of armor.
Otherwise, armor is the only real option.
If it's an omnivehicle that I'm not designing fresh so I can tweak the armor and it has an odd half ton of podspace I'd be inclined to try to shave a ton off my config and put on ECM. Or if the odd half ton comes from ECM my inclination would be to start with ECM and AMS or ECM and BAP and design the configuration around them.