I also live in a state where it is alegal (Michigan). Since it was my first baby, I did want to have testing done. (I only wanted to homebirth if I was truly "low risk" and felt the testing would help prove that). My midwife told me about an OB who was open to working with women who had birthed with her in the past. (The other major practices in the city will drop you completely if they find out you are planning to homebirth). When I first went to see the OB, his policy was that he would treat me like any other patient, he expected that I would go to all appointments and then "oops she just didn't show up at the hospital." I was fine with doing that because he seemed very supportive of natural childbirth and if I ended up needing to choose hospital birth, I would already have an established relationship.
However, about halfway through my pregnancy, he got a lot of pressure from the OBs who back him up--he is in practice by himself so it he can't make it, they were refusing to cover him. In the end, he decided to continue seeing women who were planning on having homebirths on a "consultation basis" basically all the appointments that would have testing associated with them 12 weeks for heartbeat and labs, 20 weeks for ultrasound, 24 for GTT, and 35 for GBS, etc, (maybe more but I just can't remember). This worked out really well for me because I felt like I was truly making a fully informed decision, but didn't have to drive 45 minutes go to all the other worthless appts--IMO because all they did at those appts were the same things that my MW did--BP, fundal height, listen to heartbeat, ask if I had any questions, etc.
I know many women don't say anything to the OB, but that felt like lying to me and I wasn't comfortable with it. Perhaps you could find an OB who might be open to a consultation relationship like mine decided upon. Or you could always say "I'm still deciding whether I want to deliver at the hospital or at home" that way you could wait until after the ultrasound (or whatever other testing you were interested in) results came back and then say, "based on these results, I feel comfortable having a homebirth, thank you for providing me services, but at this point I would like to transfer my care to the homebirth midwife"
I hope that helps!