akuperma
Even if you dont define homicide as any killing even lawful (As some (perhaps most) dictionaries do, your statment “The halachic approach is that this is still homicide, but it is justifiable homicide ” is still wrong.
This has been discussed at length here before but here are some differences recapped:
1) homicide carries death penalty bemeizid or galus beshogeg. Abortion carries a financial penalty
2) A kohen who kills can not duchan (even if the killing was justified) To the best of my knowedge a kohein who aborts can duchen.
Bottom line is I’m sure most would agree that we would want a competent Rav to decide on each case whether abortion was required/allowed or forbidden. I dont think anybody would argue on that point.
Obviously this isnt an option. The next best thing we have is as simcha613 outlined