Most of President Donald Trump's immigration policies have been both harsh and ill-advised. Trump, who campaigned in 2016 on a vow to limit immigration to the U.S., has seemed to be doing his best to keep that promise.

However, so far, Trump has been nibbling around the edges, unable to touch the main pillar of U.S. immigration — the green-card system. In 2017, the U.S. granted more than a million lawful permanent residencies, a number little changed from recent years.

Although Trump can try to limit this number via administrative measures, changing it substantively would probably require an act of Congress. In 2017, Republican Sens. Tom Cotton and David Perdue introduced a bill called the RAISE Act that would have cut immigration levels by half, but it didn't pass. Now, with Democrats in control of the House, getting such legislation through both houses of Congress seems even more remote. The core of the U.S. immigration system looks likely to remain intact.

But Trump recently released another proposal for reforming legal immigration that deserves some consideration. Designed by Trump's son-in-law Jared Kushner, the bill wouldn't reduce overall legal immigration levels; instead, it would shift green cards away from family sponsorship and the lottery now used to ensure geographical diversity and toward skills-based immigration. It would also include measures for increased border security, including Trump's long-sought border wall.

The idea of shifting to a more merit-based legal immigration system is a good one. Because the American public as a whole demands some sort of numerical limit on immigration, it's probably good to make sure that a high percentage of those immigrants have employable skills that will allow them to thrive in the U.S., and to help the U.S. maintain its technological dominance. Skilled immigrants also tend to come with big fiscal benefits for cash-strapped local and state governments:

Emigrants also tend to be a boon for their native countries, since they and their descendants often transfer capital and knowledge back.

The U.S. regime now is tilted less toward immigrants with skills than the systems in Canada, Australia and New Zealand. The details of the Trump-Kushner proposal are still vague, but it promises to bring the skilled percentage up to 57%.

If done right, that would be a good idea. The current system isn't bad — the education levels of U.S. immigrants have gone up a lot in recent years all on their own. But Canada's system works great, and the U.S. might as well copy its success. Skilled immigration is also extremely popular with the U.S. public.

Some will inevitably leap to defend the sanctity of the present system. But there's no deep moral reason that the U.S. system is so heavily tilted toward family sponsorship, which is largely an accident of history.

In 1965, when the outlines of the current immigration system were put in place, Rep. Michael Feighan of Ohio was worried that the new law would lead to too much nonwhite immigration. So he insisted on increasing the percentage of slots for family sponsorship, reasoning that they would mostly go to the European family members of white Americans. Of course, things didn't turn out that way. But it's important to remember that the U.S.'s family-focused system is the result of a policy that was racist by design. (It's also worth noting that a shift toward skill-based immigration, such as the one proposed by Trump and Kushner, would draw mostly Asian and African immigrants.)

Although the basic idea of a more skills-based system is a good one, the devil is in the details. Most family-based immigrants to the U.S. are the immediate family of U.S. citizens, and who are thus not covered under the quota system put in place in 1965. If the Trump-Kushner plan would bring citizens' immediate family members under the quota system, then it should be regarded as a non-starter. Also, preventing permanent residents from bringing their own spouses and children over, as some predict the plan will do, would be a very bad change. Limitation of family sponsorship immigration should be done only by reducing the number of visas allocated toward siblings and adult children.

But instead of rejecting Trump and Kushner's plan, Democrats should give it a fair hearing. If the details of the plan are reasonable, the Democrats should consider cutting a deal — relief for undocumented immigrants facing deportation, and a path to citizenship, in exchange for border security and a rebalancing of legal immigration toward merit and skills.

That deal, which would be similar to a broad immigration reform proposed in the Senate in 2013, would have the potential to make the U.S. system better for the next century.