In the _settleAuction function of the AuctionHouse smart contract, setting the builder and purchaseReferral fields to address(0) within the IERC20TokenEmitter.ProtocolRewardAddresses struct raises important considerations. 
https://github.com/code-423n4/2023-12-revolutionprotocol/blob/main/packages/revolution/src/AuctionHouse.sol#L403-L407
This design choice might align with the contracts current requirements if no rewards are intended for builders or referrers. However, it potentially limits future flexibility and adaptability to new features. While it might offer gas savings, the implications on the contracts functionality and the ecosystem should be carefully evaluated. Moreover, such hardcoding should be transparently documented for clarity and understanding. The use of upgradeable contract patterns provides some leeway for future modifications, but its crucial to balance immediate simplicity against long-term contract evolution and security.
