You won't ever get a majority of the population to agree to this view. If you hold staunchly that all the way up until 40 weeks women should be allowed to abort, you will lose at least 75% of the vote. At some point the fetus is developed enough we have to consider its life, regardless of its current location.
I think we could push viability as a compromise for everyone. That's around 21-24 weeks, depending on what is considered acceptable potential life chance. Conservatives will say that's too developed, some progressives will claim your view, but I think most would at least compromise that if we could safely take the baby out, that should be the legal option at that point. That also gives the mother a lot of time to consider her options.