They would need "type approval" by someone qualified to give that level of approval. Most engineers who approve mods can only do "one off" mods, they can't endorse "type approvals". Places that can do type approval are places such as ARB (I believe), HSV, Walkinshaw engineering, that mob in Mildura I think (Peter Dichera - spelling??)...takes a LOT of investment to get the necessary quals and all the gear together. And then there is the type of "type approval" you can do....for example, someone might be ramped up to do type approvals for exhaust emissions for a few different models of vehicle for performance chips (keep it all legit)...another might be kitted out to do type approval on bullbars, but don't have the skills or equipment to even consider suspension for example...HSV can approve certain mods on commodores and one shape (two door) Astra, but that's all....you get the idea I'm sure - it's a VERY limited and VERY well locked down process from what I understand. But that is only my understanding which could be wrong...
It's a damn complex situation.
My thoughts are that your only REALISTIC approach is the one-off modification approval by an engineer.