The “merit based” immigration part is clearly demagoguery. The legal US immigration is already a merit based system for skilled workers, even more so than those called “merit based” like Canadian and Australian. There is family sponsorship, investors etc. but the lower skilled legal immigration doesn’t exist, period! Current limitations are due to quotas and processing backlogs. Does he want to copy from Canada or Australia? Than it means a substantial increase in quotas and a bigger government, hiring more government employees, creating more policies and departments. The increase in quotas might cause job shortages and lower wages (for US workers too!) and more people using government support (new immigrants included!).
I would also expect that the best skilled workforce would be less interested to come if they expect hostile attitudes. It’s not like every brown immigrant should walk around in a T-shirt “I’m not a terrorist”.
UPD: I forgot the Diversity Lottery (is it still around?). But 1. I believe, the talk about cancelling it was under Obama 2. the quota is smaller than for skilled workers 3. the requirement is at least a high school diploma, but in practice winners are required to bring a certain amount of money, which means they fare reasonably well professionally. At least, I don’t know a single winner without a college degree.