I don’t think the solution is as simple as suggested for a number of reasons, including:
If the UK made itself significantly easier to access, it could become a more attractive destination than many others increasing volume.
Those who are ineligible or fail the process could continue to use traffickers. Of course those that fail should be subject to removal for but that is still not an easy process.
Processing centres may not be able to handle the volume meaning backlogs appear.
There is also the practical question of housing, public services and employment. Any expansion would need to consider whether there is enough capacity, particularly given existing pressures such as housing shortages, youth unemployment and the impact of automation/AI on future jobs.