Can't vouch for Aapo, but as long this is on-topic in regards to optimizations (available/possible in near future) and compiling seems totally fine for me. For on-device compilators this would be an awesome improvement - more space for libs, more memory (less restarts when compiling things that take >700mb of memory).
Having no-clue really about the underlying mechanics, but the few pdfs out there do hint at ~20% more space (or ~6% with speed increase), so would love to see this happen (all the above posts point to this being enormous project though requiring refresh of the whole system). If someone has an idea how to get this done, please share. I am willing to test all the closed packages compatibility with newer libstdc++/gcc, if someone knows how to approach this.