If there were a situation in which bitcoin must have a dynamic block size limit, it would be superior to have the block size limit based on a sat/vByte basis. If the cost to include 200 bytes in a block becomes too high, the block size limit will increase, and if the cost to include 200 bytes in a block is too low, the maximum block size will decrease.
The problem with this proposal is that we don't know the real value of the fee, if the price of btc is high then the fee will be too expensive, if the price of btc is low then the price per vByte will be too low, we can determine a percentage but we can't determine btc's price.
Using percentage also flawed since block reward changed every 4 years.
Writing a BIP is something I might consider...
Don't forget to follow the procedure on BIP 1 and see BIP 10x (since it's mainly about block size).