As a consequence of Brexit, a new points-based system will be created. Guidance on this can be found at: Living in Europe - GOV.UK (www.gov.uk). See also: Living in country guides - GOV.UK (www.gov.uk); The UK’s points-based immigration system: information for EU citizens - GOV.UK (www.gov.uk) and UK points-based immigration system: further details - GOV.UK (www.gov.uk)
There is extensive web-based guidance for caseworkers under the points-based system, much of it linked from: https://www.gov.uk/government/collections/working-in-the-uk-modernised-guidance
Guidance for sponsors is on a separate link from the UKVI page. Click on Sponsors, which takes you to: https://www.gov.uk/government/collections/sponsorship-information-for-employers-and-educators
You can also read about the work of the Migration Advisory Committee, and read the minutes of their meetings, at https://www.gov.uk/government/organisations/migration-advisory-committee.