
I ended up liking both versions equally well. Now, Original Kenna appears in "doll" photo scenes, and New Kenna appears in "action figure" scenes.
Recently I've been revising some of my 1/6-scale pirate figures. Margot'chelle Rumscupper got a complete makeover, including costume and head sculpt:

Original

Revised
The new head sculpt is sufficiently similar to the old one that it seems plausible. The original head sculpt was also being used for a different character who now gets to keep it permanently.
A third 1/6-scale character I've been having trouble coming up with a permanent look for is a scientific field researcher named Ellie Fields. The character was originally created by an online acquaintance, and I've been trying to emulate (copy) what he did, but the original pieces are no longer readily available.
Ellie started out looking like this:

Ellie v.1
Then she evolved in to this:

And then... I gave up and Ellie No. 1 became a pirate...

Dread Pirate Bethany Blood-Thunder aka the former Ellie Fields No. 1
... and Ellie No. 2 was banished to a convent:

Sister Albatros of the Convent of the Sisters of Little Mercy aka the former Ellie Fields No. 2
I'm abandoning the Ellie Fields project, at least for now, because what I have been able to come up with has never seemed to fit the character.
Have we reached the TL:DNR stage yet? There's one more character who appears in, or will appear in, a military story: the mysterious and aloof Fräulein Erde Gräfin Spitz-Ohren, scientific advisor and consultant in occult arcana to the Ahnenerbe.
This character has gone through several iterations:

Version 1 - too clunky looking

Version 2 - too kinky fetish looking

Version 3 - costume didn't fit very well and was too fragile and the Pullip doll wanted her dress back

Version 4 - latest incarnation as of last week with kind of a Dieselpunk vibe
At least Fräulein Spitz-Ohren kept the same head sculpt, which has made the iterations easier to accept. For me, the head largely defines the character.
Coincidentally, a little over a week ago I was having this same philosophical debate with myself over "repurposing" dolls and figures who have become established characters. I posted the following caption on Flickr:
Former pirate Beverly Blood-Thunder has retired from life at sea to become a permanent Cuban Rebel Girl. The new pirate figure pictured here [above] was previously an incarnation of Royal Kadath Society character Ellie Fields, but since Ellie was updated to a more accurate head sculpt, the former Miss Fields has stepped in to fill the vacancy in the pirate crew, adopting the name Bethany Blood-Thunder in acknowledgement of her predecessor. (The second Ellie has since been similarly repurposed, joining a convent as a nun.)
Do any of you ever find yourself becoming attached to the physical embodiment of the characters you create, as in, if you decide to "repurpose" parts of a pre-existing character, do you feel a need to "explain" or "justify" the change, at least to yourself? In this case, both "Beverly Blood-Thunder" and "Ellie Fields" appeared only briefly in now-forgotten photo-story installments. I'm sure nobody remembers them other than me, yet I feel I can't just let them disappear without some kind of acknowledgement.
It is reassuring to see that I am not alone in my angst over physically changing established characters.