There are units that grow with your general. These units not only survive many battles they can also survive being decommissioned. A few ideas to celebrate these feats:
1. Create a way to label or name unit cards for distinction
2. Create or generate more distinct type of unit card grafx for units you feel are deserving

Recap: It would be nice to label units based on xp gained vs xp given because of tech.

Just a thought.