Update to 0.8
MoR 0.8 is compatible with 0.7.8+ versions - including the assignment of traits to existing slaves. It's still recommended to start a new game if you want to get the complete 0.8 experience, however!
There might also be some issues with birthdays - meaning that your slave's coming birthday might execute relatively close to her last - as there's no way for me to align the new aging system with the old one.
How to update
Save your old 0.7.9.4 game inside your House, load it with the 0.8 version and IMMEDIATELY press the Update to 0.8 button located under End Day.
Doing so will inject 0.8's new variables into your save and reconstruct Aria's quest - adding the 23-day countdown before you're able to purchase her.
How to assign traits
There's now a Trait Roll button in the new Slave Control Menu. This button offers 25 re-rolls and only appears for your first primary slave (top left). Shuffle your annex slaves to this slot in order to assign them all with traits. NOTE! Pressing this button will erase all trait progress, titles, allowances and defiance!