What problem does this feature solve?

In this example, three chunks (entry.js, foo-DC2v_zmv.js, foo-CM5cnA2r.js) are generated.
REPL
But foo-CM5cnA2r.js just re-exports everything from foo-DC2v_zmv.js. In this case, all import to foo-CM5cnA2r.js can be replaced with foo-DC2v_zmv.js. I guess we can also take preserveEntrySignatures into consideration here.

What does the proposed API look like?

Not an API change