Update for the community: we developed a contract to bridge ERC20 tokens from Polygon to Mainnet. This is a publicly-available tool for managing treasury assets, in addition to the Aave Swapper and Strategic Asset Manager.
Currently, Polygon assets cannot be withdrawn from Polygon and thus, assets held on that network cannot be used as part of a treasury management strategy. The Aave Polygon-Mainnet ERC20Bridge is a bridge that lets the DAO send funds from Polygon to Mainnet to best manager treasury funds. The main functions on this contract are to bridge from Polygon, and later on to confirm the transaction on Mainnet.
More details can be found here: