[BIP-295] Fee Discount for CowSwap Solvers

https://github.com/BalancerMaxis/multisig-ops/pull/195

Motivation

Balancer contributors have recently been exploring ways to increase non-toxic flow through the protocol. One opportunity which has presented itself is to leverage our close partnership with CowSwap to implement a fee discount when solvers route trades through Balancer liquidity. This would be done by granting the role for calling setSwapFeePercentage to the GPv2Settlement contract - then solvers would pass in interactions which lower the fee on the pool, execute the swap, then return the fee to the previous value. The swap fee could be lowered in this manner by around 50-75% to enable a significant increase in “good flow” to Balancer pools.

Most of Balancer’s protocol fees are generated from yield rather than swaps. There is a chance this proposal leads to more swap fees but even if it does not, one of the most important goals for the Balancer ecosystem is to grow our DEX volume market share. This is likely one of the best chances we have to move the needle on that on Ethereum.

Risks

The Maxis will retain the ability to call setSwapFeePercentage on all pool factories so if something unexpected happens and fees are dramatically lowered or raised globally by accident it can be fixed very quickly by the Maxis. Governance can also revoke this role at any time in the future through a future BIP.

Specification

If approved, the DAO Multisig eth:0x10A19e7eE7d7F8a52822f6817de8ea18204F2e4f will interact with the Authorizer 0xA331D84eC860Bf466b4CdCcFb4aC09a1B43F3aE6 and call grantRoles with the following arguments:

Roles: 0x3697d13ee45583cf9c2c64a978ab5886bcd07ec2b851efbea2fced982b8f9596,0xc065d550fa98abc242b6baf98e7b2063590675f1ddd81bdb9ea8d8f5c5d52f98,0x7b09f4b61ccfe85436161b0223489b187d9f9158c542b5e6105df147afc78aca,0x15d3918ca8f9895d8906a780f5f402d32707bada7b1b5e7b21b7351257103a35,0xcf5e03a737e4f5ba6d13e23f893a1e0255b362d8ce22e9568e1565fcf92789c7,0x6c3a14f10cbcc5a3f4d0e4e8ad279e7a842735ab188e2b13fb84c6542cc3320c,0x78e9adfe5f05d7114a59d0870d78971192f871f57bb36e2aff2edbe75d425844,0xdee20d81c6075dcc437dbaaf02d316ab255cfcae4a154e04b17abdebc70a5b48,0xd8638fc873fb8c5c0e67c437099a19eb0546fb439dab8babff44196f11d44831,0x1a88f724f61d4985675e65a2ba85b2a985d250dac00d27e06303f4cdabc906ae,0xa5547190e3d59f2bfeb4174ca3454b2f2acaeed644bc7ad7018014516f73f2bd,0x0acc45f3ac7c04369514ee383aad82d5c1eef484fbf9ca5f6d87ad5c5859da40

[details="Which correspond to the roles for calling setSwapFeePercentage on the following pool factories"] WeightedPool v1

WeightedPool2TokensFactory

Stable Pool v1

Metastable

Stable Pool v2

ComposableStablePool

WeightedPool v2

ComposableStablePool v2

WeightedPool v3

ComposableStablePool v3

WeightedPool v4

ComposableStablePool v4 [/details]

Account: 0x9008D19f58AAbD9eD0D60971565AA8510560ab41

Which corresponds to the address for Cowswap’s GPv2Settlement contract