I'm not sure I would consider it heretical, perhaps because I am not sure I would take Bride of Christ as literally as you seem to be (something I may be in error over). It would seem not to be heretical to say He could have married had He chosen to (though keeping in mind the Church clearly teaches He did NOT marry), because He is a human being, and marriage is a perfectly legitimate thing for a Christian. There is no shame in marriage. However, I do agree that it would not have been helpful to His mission, which is why He didn't.
Ultimately I don't see questions such as these as important, because the important thing is the the Lord did not see marriage as helpful to His goals on Earth (for a variety of reasons, most of which we can only speculate on).
However, now that I've typed this, I also thought of the fact that for any woman to have married Christ, she would have married the Godhead and had intercourse with the fullness of God, in Christ. Perhaps this, then would have been heretical? Either way, I think the above sentence still stands, the important thing is that He did not marry