Thanks David for the great article. When it comes to cutting embodied carbon the simplest technical answer of course is to build less - the City of Vancouver has committed to a 40% reducting in embodied carbon by 2030, but nowhere can I find how this will be measured, and whether absolute increase in floor area is considered - if anyone has the answer to this I’d be keen to hear it. Anecdotally, it is very hard to convince politicians to build less, I remember when our recommendations to renew municipal infrastructure were overlooked to build a stadium, which subsequently bankrupted the local government, and they still needed to fix the pipes!
I like the LBC approach that requires projects to be on brownfield sites, and must incorproate some material reuse, although this could be taken further. Ultimately with widespread renewables it may be possible to sequester carbon in our built environment, but we are nowhere near to balancing anthropogenic emissions, and the volumes required are enormous. Hopefully a silver lining from the pandemic will be more telecommuting, less commercial real estate demand, 
a rejection of neoliberal economics and unending consumption.