The first proposal is to make probing free, meaning no liquidity would be locked up, and the second is to require senders to pay for failed payment attempts. However, a concern is raised about the potential for malicious routing nodes to succeed the probe and then intentionally fail the payment to collect the fee. Another participant in the thread points out a similar proposal made in a previous email and adds additional ideas. Overall, the thread discusses potential solutions to improving upfront payment fees in Lightning Network transactions.