I feel veterans are a bit undervalued in this game. Free Agency is always littered with vets with good skills, but they're really tough to sign and they're worthless to teams in rebuilding. Here's two ideas to help balance that out a bit:
1) Announcing Retirement - Take the ambiguity out of signing/resigning a vet. In the NFL, its not uncommon for a vet to announce he'll retire at the end of the year/end of his contract/in two years. Have some vets announce their retirement to replace the retirement %. Alternatively, something to define how long the 9+ year vets should be signed for.
2) Have young players learn from vets - Progression is currently split between HC, Coordinator, and Position Coach at 50/30/20. I propose ~5% should be taken away from head coach and added to Veteran presence. This could be tweaked as needed.
These two things would help