Please note that this is a community forum and not a support forum. There is no guarantee that you will hear from Elastic support at all.
Which exact version are you using?
Why not perform an in-place rolling upgrade instead as that likely would be a lot easier (even if it were to require multiple upgrade steps)?
This sounds like a completely custom approach that I doubt anyone else have tested or documented. It may work, but it is on you to ensure that you test and verify the validity of the approach properly.
If you are looking for a supported and recommended approach I believe you should perform an in-place rolling upgrade. Unless you have indices created in Elasticsearch 6.x this should be relatively simple and not require reindexing if you just move to Elasticsearch 8.19.