How to reduce index mapping fields while keeping data continuity

my issue is like this.
I am trying to switch a dynamic mapping to static without impacting the users.
We have many text and keyword fields which are redundant.
the trick is... if field A has both A (text) and A.keyword (keyword)
and the mapping looks like:

'A': {'type': 'text',
  'fields': {'keyword': {'type': 'keyword', 'ignore_above': 256}}},

how do I keep only the A.keyword field (delete the A field) without impacting the structure and naming of the fields?

How are you approaching the broader changes without any impact?

@warkolm
I'm sorry. I don't follow.
what do you mean by broader changes?

You can't make these changes without a reindex. You can use aliases to reduce the impact to users, but there's no guarantee of no impact.

@warkolm ok. thanks