While I see your aim I believe this will have more negative effects for the ecosystem than positive.
The biggest few I can think off:
- Devalues non modern sets even more after past proposals also devaluing them due to rentals being targeted
- Will cost a lot in limited Splinterlands resources to implement and monitor
- Tells people investing any area of the game can be targeted by the DAO for reward reduction (Rentals, LP rewards, Ranked). This is not the signal potential, or current, investors look for
- Sets a precedent players who rent are not seen as an important part of the ecosystem
- Implements a historic system previously deemed to deter new players