You will not find a single Jew from across the spectrum of liberal to haredi Jews who would accept a Messianic Jew as truly being Jewish.
The JEWS who do accept Jesus as the Messiah would disagree with you -- AS JEWS. They will maintain by all other standards -- that they are Jews (and rightfully so), while they do accept Jesus as Messiah. They are a witness against other Jews.
The Messianic Jews have yet to convince *any* other Jews of the validity of their Jewishness--telling me that *they* think of themselves as Jewish is neither convincing nor surprising. The question of who is a Jew, is of course, an extremely complex and controversial subject in Judaism, with a huge set of halakhot and responsa on the subject. Matrilineal descent and standards of conversion are two of the hot topics of today. The question of "can someone believe in Jesus as the Messiah and be Jewish", however, is not now and has never been, a topic of debate. The answer, according to every Jewish authority, is no.
Jews who, like "those of the ruling religious class" that you mentioned who "accepted [Jesus] as the Messiah" were and are considered by other Jews to be heretics, to have stepped outside the boundaries of Jewish faith, by their actions.