This would be to honor a deceased mother so [name_u]Jean[/name_u] seems best in the middle. WDYT of it? Is it awful? Maybe [name_f]Jeannette[/name_f]?
I think [name_u]Jean[/name_u] is fine, especially as you are using it to honour someone.
I think names that end in IE sound more ‘country’ with [name_u]Jean[/name_u] e.g [name_f]Ellie[/name_f] [name_u]Jean[/name_u] vs. [name_f]Eleanor[/name_f] [name_u]Jean[/name_u]
[name_f]Jeannette[/name_f] seems more ‘dated’ to me. Though I am not in the US so it may be different there.
Agree completely with pp. I like [name_u]Jean[/name_u], and I don’t immediately think “country” unless the rest of the name is also country-like.
I think [name_u]Jean[/name_u] is a nice middle, it’s a lot more interesting than [name_f]Rose[/name_f]/[name_f]Grace[/name_f] and not particularly country. Not more so than [name_f]Mae[/name_f] or [name_f]Jane[/name_f], which I like too. [name_f]Katie[/name_f] [name_u]Jean[/name_u] is a little bit country but not unusable. [name_f]Katharine[/name_f] [name_u]Jean[/name_u] is fine. [name_u]Billie[/name_u] [name_u]Jean[/name_u] feels almost joke-level country but were you really going to name a girl [name_u]Billie[/name_u] if you didn’t like country names? [name_f]Sybilla[/name_f] [name_u]Jean[/name_u] is back to being fine.
[name_f]Jeannette[/name_f] is kind of awful though. I don’t think there’s a single -ette name that I like.
It would be [name_f]Seraphina[/name_f] [name_u]Jean[/name_u] 
I think [name_u]Jean[/name_u] is fine. It doesn’t strike me as ‘too country’ at all. I much prefer [name_u]Jean[/name_u] to [name_f]Jeannette[/name_f].
[name_f]Seraphina[/name_f] [name_u]Jean[/name_u] is incredibly beautiful. I think of elegance and grace - not at all ‘country’ to me!
[name_u]Jean[/name_u] is a family name for me, too. I might have to add [name_f]Seraphina[/name_f] [name_u]Jean[/name_u] to my list! 
I think its nice as a middle, especially if its honoring someone. Though I might be biased, one of my favourite combos is [name_f]Margot[/name_f] [name_u]Jean[/name_u] (for two Aunts). [name_f]Jeanette[/name_f] actually seems more dated to me. [name_f]Seraphina[/name_f] [name_u]Jean[/name_u] is lovely.
A counterpoint to previous posters, I think [name_f]Jennette[/name_f] is lovely, although I suppose it is from [name_f]Janet[/name_f] rather than [name_u]Jean[/name_u]? I also like [name_u]Jean[/name_u]-marie. But with [name_f]Seraphina[/name_f], maybe [name_u]Jean[/name_u] is enough.
I do think [name_u]Jean[/name_u] can come off country in the midwest US (were you asking this in a previous forum ? I think I just said this to someone else), but you shouldn’t let that stop you for a sweet namesake.
Maybe it’s the country girl in me, but I love it. It’s so simple and cute.
[name_f]Do[/name_f] not use [name_f]Jeanette[/name_f]! [name_u]Jean[/name_u] will be fine.