The first question is how much expression is omitted? It may be a part of a clause, an entire clause, or several clauses. The surviving syntax and context identify the level of omission.
ExtentWhat is missing?Typical case
Clause constituentOne element or modifierPossessed term, described noun, object, subject
A clauseA complete predicationConditional answer or explanatory cause
Several clausesMultiple stages of an eventA rapid narrative transition
The reconstruction helps reveal the omission; the rhetorical effect must still be assessed in the actual wording.