Also, after a verification that the Visa recipient is working at the given salary for at least two years, then the they can apply for green card irrelevant to who their current employer is (as long as they are employed and earning at least similar salaries to what they did when they got the visa).
Switching jobs (as long as it is the similar profession/pay), should not reset the Green Card process. This will remove the current defacto "Indentured servitude" state that most H-1B visa holders find themselves in.
There are many ways to improve the current system (without changing the quotas), to benefit the country itself, and not large corporations, but right now there is no direct personal incentive for lawmakers to do that.