Not sure what you are trying to do - are planning to make a plugin for others to use ?
If so you need the Plugin to make the tables.
Otherwise If the table exists installing the plugin should not overwite the table
(but take a backup just to be sure there are no problems)
And if the Schema matches the table the Plugin should be able to continue to read and write data in the existing table.
No, the plugins will not be distributed.
I have 10+ stores live today, with custom tables in different plugins.
When i'm upgrading a test-store to 4.3 i'm getting issues since the tables are already existing. So my question was if i'm supposed to match the scheme file to the table, or if it exists a reverse engineering. I know EF used to have this in VS, so you could generate files db model files based on an existing db.