Napoleon conquered half of Europe and had a very large army backing him up. The first Holy Roman Emperor Charlemagne was in a similar situation.
"Herr Hitler, You want to be German Emperor. You and whose army?"
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If he declared himself emperor in 1941, perhaps after Wilhelm II died, that question would answer itself.
However, it just isn't going to happen for all the reasons previously listed.
Hitler had neither an emotion nor political need for a monarchy. . Being Fuhrer gave him everything he required.
He had no desire to found a dynastic leadership; a system he regarded as inherently weak.
Furthermore, declaring himself emperor would have undermined his own position whenever he did it, both at home and abroad. No one questioned the legitimacy of his being Fuhrer, which had all been done constitutionally (just about). Becoming a royal, however, is more than about the legalities. Actual monarchists - of which there were plenty surviving - would have viewed him as illegitimate whatever the legal steps taken: Wilhelm or his sons and grandsons were the only possible emperors available. Had he sought the crown, he would have strengthened their position by reintroducing their role, while diminishing his own.