Go for it! It’s in the middle, so I don’t see any harm.
I’d vote [name_f]Jacqueline[/name_f] or [name_u]Jackie[/name_u], to be honest. I love that you are honoring!
I think you should definitely use it in the middle spot. I’m all for using honor names. I have a friend whose initials spell ‘[name_m]JAC[/name_m]’. She went by [name_m]Jac[/name_m] for awhile in high school so I know it can work. Everyone thought it was cool. I would spell it [name_m]Jack[/name_m]. Changing the spelling just makes it confusing because it’s still pronounced the same.
I’m pretending that it is MY middle name and thinking of it as to how your daughter would feel about it. I think it’s risky from that point of view. Otherwise, it’s just the middle spot, and you could use just [name_m]Jack[/name_m], but your daughter is likely to appreciate [name_f]Jaclyn[/name_f] or [name_f]Jacqueline[/name_f] more, and you would still be honouring family. Another thought is that perhaps the family members’s actual names are [name_m]John[/name_m] with nn [name_m]Jack[/name_m], then your daughter’s mn could be [name_m]Jona[/name_m] (pronounced [name_m]John[/name_m]-a)
I think giving it a more feminine looking spelling would work better. Visually it just looks kind of unflattering next to such a feminine first name with a feminine spelling.
I understand that it is for honour reasons - but [name_m]Jack[/name_m] really is a boys name - save it for a future son? Or use one of the alternative suggestions on here such as [name_f]Jacklyn[/name_f] which adds a touch of femininity
I would not use [name_m]Jack[/name_m] for a girl, I’d personally feel awkward if my middle name was [name_m]Jack[/name_m]. Perhaps [name_u]Jean[/name_u], Johna, [name_f]Jacqueline[/name_f] could work?
As a side thought, maybe a name with the same origin or meaning as [name_m]Jack[/name_m] could work as an honor name?
It only works if it’s short for [name_f]Jaqueline[/name_f]