If John 3:16 said "whosoever is one of the elect that believes will not perish but have eternal life", then your point would be valid.
But since you added a specific identifier in your example, it is not relevant to my comment about the phrase "whoever" in John 3:16, where there is not specific identifier.
That's incorrect. The syntax of both John 3:16 and my examples is: All {relative_pronoun relative_clause_predicate } main_clause_predicate.
The "identifier" I "add," namely "Is a man," and the "identifier" in John 3:16, "believes," perform the same grammatical function.
But since you seem to believe that "Is a man" and "believes" are syntactically different (Probably because one of them is an intransitive verb and the other is a copula with a predicate nominative, which is syntactically irrelevant to the nature of relative pronouns) I'll give you a substitute example without the PN. "Whoever conceives will bear a child."
I read the original language of the NT to find out how to find the Greek words in my lexicon. iow, I lean on the experts.
This is the boast of those who don't understand exactly how much effort is required to actually begin to conceive of Greek or grammar correctly. It takes eight college credits to learn basic grammar, and every graduate of first year Greek becomes a terror with a lexicon and his Mounce. You and they aren't "leaning on the experts" when they mangle translation. They're misusing the resources the don't understand. Thereafter it takes eight more credits of Dan Wallace before an individual begins to be able to exegete Greek safely.
This is a laugh. I know well how the Greek reads. Yet most of the translations seem to understand better than either of us what the Greek MEANT.
To listen to your rendition suggests the translators failed to get it right while your rendition is right. What are your credentials in Greek?
You're missing the point. My rendition isn't an alternate sense to the sense provided in the translations as they stand. My rendition is the sense of the translations as they already stand. In the English language, "God loved the world thus: He gave His only son so that all believers will not perish but will inherit eternal life" is
exactly interchangeable with "For God so loved the world, that He gave His only son, that whosoever believeth in Him might not perish but may inherit eternal life." Some of that apparent distinction can be attributed to the fact that proper and colloquial English in the 20th-21st century are more variant than the colloquial speaker might believe. But at no point in our tongue's fifteen hundred year history has "all" plus a relative pronoun implied that all humans are capable of being predicated by the predicate of the relative pronoun.
My credentials are a degree in Classical languages, consisting of six semesters of Greek and four of other classics, plus the high school equivalent of two college semesters of Latin, followed up with continuing personal studies equivalent to probably eight semesters in various non Indo-European languages. If you add up all the years I've seriously or semi-seriously studied all my languages, I'm counting up to about fourteen years of practice in language and linguistic theory.