I think the best basic income schemes have a negative progressive income tax basis to them. You lose the basic income as your regular income increases and at some level of earned income you don't get any basic income.
The main issue I have with that suggestion is that it destroys one of the large benefits of UBI/mincome--the removal of bureaucracy overhead, where the removal also frees up money for use in mincome.
With standard mincome, you have a questionnaire that is no larger than a regular SS card:
1) Are you 18?
2) Are you American?
3) Do you have a pulse?
The end. Say yes to all three, provide whatever documentation is necessary to qualify the answers, and you're done.
Putting any stipulations on that just makes the program require more money, perhaps even more than might be "saved" by not paying anything to those with sufficient income. You have to now list your income for last year, projected income for this year. If you lose your income you have to prove that to receive UBI again, and probably every single recipient would have to do the same. Plus, making it reliant on anything specific makes it far easier for more specifics to be applied, and then very few will receive mincome and we're all worse off for it.
This provides a work incentive
Now I think you might be missing a huge reason for mincome: work is unnecessary. Not just unavailable to a portion of the population, but much of the work that is done is unnecessary. There is not enough work that actually needs to be done to regularly employee the people we have, and such a gap will only increase over time.
A person's existence shouldn't be completely dependent on their interest in working. Heck, how many hundreds of thousands, or perhaps even millions, already earn money without actually doing any work?
For one, I think employers generally fear any world where unemployment isn't an existential threat for employees -- I think it radically reshapes the balance of power.
On this I agree, and is a huge reason I support it (I work under the assumption that we would implement universal healthcare before universal income). If employees have a lot more freedom in their job choices--or even having a job at all--the employers can no longer lord over them. At the same time, companies will also be freed of a lot of stuff: minimum wage is dissolved, unions will become far less necessary, a lot of labor laws might be relaxed (or at least fewer implemented.) Businesses will have far more direct pressure from employees, potential or existing, so the government won't have to act as much to balance out things.
will also be freed of a lo Immigration is a real problem -- how do you contain a basic income system to the basic margins of your economy?
Make it based on citizenship, held for at least six months. This means that the people who immigrate are either those in moderate-high demand, who have well-paying jobs lined up that they don't need UBI, or that already have sufficient funds to survive until they meet that requirement.
Illegal immigrants? This is certainly a problem that needs addressing, but it's not going to be some sort of drain on an UBI system. In fact, it might help with that issue: Illegal immigrants are unlikely to apply because it significantly increases the chances of being discovered and deported, and without minimum wage in place it becomes far harder for them to survive so they have less incentive to come over. The Department of Basic Income would likely have an investigative division to snuff out fraud and application by illegal immigrants.