Hi Hem,
If your needs rework Custom HCM Report on Hana and take advantage of HANA, first, you should be install SAP Hana Studio or Eclipse Studio and then you can take your Z programs and convert it.
Now, i think not is just Best Practices, basically, you will use the power of HANA.
In reference to FM's, you will figured out what is the better FM for your scenario.
Regards,