I am a descendant of one of the six Bechtel immigrants who came to southeastern Pennsylvania in the early to mid 1700s. I've done quite a bit of research on the Bechtel descendants that remained in that area -- trying to sort them out. The name variants I have come across with these immigrants and their descendants are more to do with phonetic spelling differences. (Bechtel, Becktel, Pectal, Bechtold, etc).
I was under the impression that the suffix "heimer" meant from a place of that name. Maybe a town or village named Bechtel??
That being said, I think that DNA testing is an excellent idea. It looks like FamilyTreeDNA has a Y-DNA project for the surname Biddle/Bechtel/etc, but for that you would need a direct male descendant of your Bechtelheimer line.