Must needs be
Whenever I encounter constructs like "
It_1 must needs be
I tend to decompose it
itmust be that
it_1needs to be
rather than into
"it must be
X" intensified by an adverb "needs",
which seem to be the consensus.
There's also archaic "needs must" in which "needs" seems to be a noun and they (the "needs") actually "must":
If needs must, I'll do it.
Finally, there's other "must needs" in which "needs" acts as an amplifier and some knowledgeable people identify it as an adverb:
Shall have to
I also have just encountered a construct "shall have to":