Officially, {i} always start a new "statement", while {i JOI} or {i (tag) BO} start a new sentence. La zantufa does not differs in this point.
Allowing a full statement in nu-clause or noi-clause requires KEI or KUhO in more cases than the official grammar, and it is just like cmevla as selbrisle requires CU in more cases. This change is required mainly from a logical point of view, and incidentally for grammatical simplicity.
A statement in nu-clause has its own universe of discourse independent from the outer bridi. A full logical reasoning must be possible in that universe, but the official grammar limits the freedom of logical _expression_ in nu-clause to so-called "subsentence". I just gave the full liberty of logical _expression_ to that universe in nu-clause.
If Lojban is called "logji bangu", I think it's structure related to Logic should be more refined, otherwise "logji" should be removed from its sub-name.
As for noi-clause, the universe of discourse is the same as that of outer bridi. I don't think noi-clause must have full liberty of logical _expression_, but it is also liberated only for simplicity of grammar.
If you don't like this proposal, just don't use la zantufa. It is defined as "zabna fi la guskant" parser, not "fi do".