Note this proposal was re-created as the previous proposal did not include the AQUA auto-compound amount
On the Red and Blue planet, the current auto-compound fee is 2.5% and on Uranus it is 5%. The AQUA rewards given on top of the aggregation is always significantly higher than the cake, auto, and belt interest.
Take the BTC vault, for example, the rewards from auto/belt are currently 6.14% and from AQUA it is currently 8.09%. In this vault, we take 2.5% interest of the 6.14% = 0.1535% and then give users 8.09% in AQUA interest.
As such this current model gives more incentive for users to deposit in a vault and sell AQUA over holding AQUA as the buying pressure on AQUA from the fees is relatively low. If we increase the fee to 5% we will be burning twice as much AQUA and it will increase the buying pressure on AQUA.