Give armor a Health Threshold based upon the materials used in the construction. Cloth will have 1-2 HT while Heavy Battle Armor should have 10. For every attack that goes through the soak of the character, subtract that amount from the Armor's HT, in addition to the WT of the character. This will cause armor to degrade fast and need to be repaired by using mechanics and armor patches. I would say that only materials like laminate or other hard armors can gain the Hardened Mod which halves the damage that is applied to the armor to increase its longevity. I would make the Hardened Mod be like Encumbrance +2 and cost 5,000 credits while taking up two mod slots.
that is way over complicating something we already have a system to handle.
It's not over complicated. In fact, it's rather simple alteration that just means tracking the armor's health. It provides two benefits, one is that the armor will degrade over time and it becomes a money sink to keep the gear operational.
While it isn't a complicated concept, it is rather involved on the bookkeeping side of things. I think this is perhaps what Daeglan meant.
I would rather simply add in a bit of a houserule that says particularly sturdy armor takes extra Advantage to activate the Sunder quality against. Like it's only 1 Advantage to Sunder laminate armor and damage it one step, but maybe your Soak 3 armors require 2 Advantage to damage one step.