Replacing a single zipper with a two-way/double zipper on jackets

I have noticed a dearth of jackets available with two-way/double zippers on the market. I love a double-zipper option even on mid-layer pieces: they allow for sitting and adjusting fit in torso-twisting and belay situations, but I cannot seem to find many pieces that feature such a setup (belay jackets being the exception, but it's hit-or-miss even there). I have considered the option of having a double-zipper added to jackets by a tailor or seamstress, and I was wondering if anyone here on Mountain Project has undertaken such a thing. Has anyone replaced a mono-zipper with a two-way? Any suggestions for having the procedure done?

Does anyone else even care? Am I a lone voice in the wilderness crying out for more zipper options!?

Thank you in advance, I look forward to hearing your replies.

I've done zipper replacements in a number of garments. It can be rather easy, or practically impossible, depending on how the garment is constructed. Quick example: some zippers these days are not sewn on but rather glued in place, similar to small pockets. I can't un-glue a zipper, or glue on a replacement. By contrast sometimes it's as simple as cutting two rows of visible stitching on the tape of the zipper and sewing the new on on the same way.