Mirror modifier merge option to optionally check if edge is boundary

with mirror there isn't much option on what to merge and weld gives often better results, adding the option to merge only vertices that belong to boundary edges would make the process less prone to face collapse along the mirroring axis center, that often occurs with verts too close to the center resulting in destroyed topology, having it take into consideration this, as an additional checkbox on the mirror mod, while slowing down the mirroring process, would make the use of it a lot less frustrating and generally easier for workflows such as retopology etc