Thanks for the response Lars. So moving a CD ABAP project to the HANA DB doesn't impact support, that's a really important distinction.
CD developers are human like everyone else, and it's fair to assume that they too introduce code which requires remediation on HANA (nested loops, SELECT *).
Since it's supported by SAP, is it reasonable to think that we could open OSS incidents for code which runs slower on HANA? Honestly I ask this slightly tongue in cheek, it's not a good way to run a migration project. 
I guess in practice, we identify together the volume of change required and create a CD work package that includes the remediation? This way, continued support would be assured?
John