is there an internal method I could use in my plugin, that would convert a string "table.column" into the respective dialects escaped equivalent? So that i would get "table.column" for mysql and whatever syntax postgres and co has for those dialects?
No. That requires parsing SQL, which is something that Sequel never does. The general Sequel way to represent qualified identifiers is :table__column.
You could probably do the following: Sequel.qualify(*str.split('.', 2)), which returns an object that Sequel will literalize correctly.