Remove RPL collateral requirements for node operators.
Instead add a platform fee, which is a percent of the validator rewards that are redirected to a RPL treasury. The fee percent can be changed at any time by vote of RPL holders in order to capture value, incentivize node operators, and remain competitive with alternatives.
An optional addition to this plan is that the fee could be negative, giving rewards from the treasury to node operators, to incentivize more to join. Or, emission of RPL can be used to incentivize node operators to join.
Presumably the treasury will eventually be used to repurchase RPL to return the value to token holders, but this does not need to be decided at this time.