It looks like Resolve 9 can play AVCHD media (without transcoding). The user interface gets a *lot* slower so I'm not suggesting it is a good idea, just that technically it seems possible now. In Resolve 8 bad things happened if I brought in AVCDH media, such as lock ups.
Note that I'm using AVCHD re-wrapped in quicktime by FCP X.
I discovered it by accident because FCP X still writes references to the original media in an export XML instead of the optimized file.