Every time I play ACE Combat, I feel that I'm processing a harem, every military hardware is a beautiful girl to me. That's what we call "the winner of life". So if every fighter transforms into a girl, or more precisely, a bishoujo, what will they look like? I'm searching references from my favorite Japanese cartoonists' drawings, maybe later I'll come up with my own opinions.
So, mainstream superfighters (fictional aircraft) for starters.
Since she is the very first superfighter in entire franchise, I always consider a traditional Japanese female, namely a Nadeshiko Yamato, is the best candicate for her “Moe/Bishoujo Anthropomorphism”. Therefore I choose Madoka Koumoto  from visual novel (galgame) "Hoshizora e Kakaru Hashi (lit. Bridge to Starry Sky)", not only because she is a miko and a template of Nadeshiko Yamato, also because default painting scheme of XFA-27 consisted by white base color and red fringing, which perfectly corresponding with a miko's standard costume: Shirakime (white blouse) and Hinohakama (red longuette).
The original cartoonist Ryohka (涼香) is really good at illustrating and character designing. I first acknowledged her drawings by light novel "Hana × Hana (花 × 華)" and quickly added her to my list of favorite Japanese cartoonists.
Can be considered as a "refined" version of XFA-27, not too dazzling and never overbearing powerful, but all around adaptable and reliable. Even you are seduced away by other aircraft with domineering powerful gadgets, she is still there waiting for you, and silently supporting you, just like a gentle and well-educated lady. So I choose Kirigasaki H. Lycerisious  from visual novel "Kiss x Demon Lord x Darjeeling", partly because she is way too gentle for a human, also because I always choose white/silver painting scheme for X-02 and she has silver-colored hair.
The original cartoonist Chikotam (ちこたむ) always does good jobs of designing characters belong to "younger sisters that trigger your protective impulses" category.
Beautiful and majestic, pure and charming, a perfect military hardware that only can be matched with a perfect girl/bishoujo. So I choose Kurara Amamiya  from visual novel "Hoshiuta (lit. Star Song)", she has everything a girl/bishoujo can dream of, your life is complete if you marry her.
The original cartoonist Fumio (フミオ) is a versitle one, potent at design every category of female characters with very high readings on "Moe Gauge".
Demonically beautiful and aggresively seductive, she blurs the border between Seraph and Satan. Thus I choose Sarasa Kuyou  from visual novel "Kiss x Demon Lord x Darjeeling", for she gives you a brand new understanding of extreme glamour (Note: Don't look into her eyes if you don't want your soul gets sucked away).
The original cartoonist Mikeou (みけおう), born and live in Hokkaido, always occupies one of top three positions in my list of favorite Japanese cartoonists. She is proficient in design "matured and sensual onee-san". However her golden era is from 2005 to 2009, and her drawings are not as good as used to be after year of 2010, which eloquently and factually proofed innovation is risky and should be undertaken with caution.
The Demon White Fang...so the best match is a demon girl...nah, demon bishoujo. Therefore Meari from comic "Tsukiyo no Fromage (lit. Fromage of Moon Night)" is chosen. She is a demon (or fairy) must feed on energies of human's good dreams to survive, much like a vampire or something. But I'm willing to let her feast on my good dreams, for her absorbs energies via kissing. Nobody can complain about being kissed by such a beautiful girl...nah, bishoujo, who is so exquisite and fragile, even can be mistaken for a doll made by a top-tier craftsman.
The original cartoonist Tinkle (てぃんくる), a.k.a. Tinkerbell, is a rare genius cartoonist (or cartoonist team) in Japan. His talents of designing female characters and clothes reach an unprecedented height.
The dark comet who seeds destructions and reaps deaths...I choose Himari Noihara from comic "Omamori Himari (lit. Scarlet Ball the Protective Charm)". Half the reason is she is a dangerous combatant and has dark-indigo hair and irises, the other half is for "omamori" means "talisman" in Japanese.
The penname of original cartoonist Miran Matora (まとら みらん) is inspired by Mecanique-Aviation-Traction Corporation and MILAN Anti-Tank Missile. He said that he never had a pet cat, but his most renowned work, Omamori Himari, is about a demon catgirl.
I always pair Fenrir with GAF-1 Varcolac, so when I select a candicate for her bishoujo form, I choose Fiyu from comic "Tsukiyo no Fromage". Contrary to Meari who has white/silver hair and resembles a princess of western style, Fiyu has black hair and is a Nadeshiko Yamato. She's also Meari's intimate friend since...well, let's say since they first met each other over a decade ago.
When I was reading comic Tsukiyo no Fromage, my nosebleed spruted uncontrollably. This is one of the most sweet and blissful comic I have ever encountered, although there's a trace of tension and uneasiness hiding behind. Upmost unfortunate this comic was never finished after two volumes, everything was left cliffhanger.
F-3 Shinden II
By some unknown reasons, I award the position of bishoujo form of F-3 Shinden II to Matsuri Shihou from animation/comic "Sola (variant of sora/そら/空, means sky in Japanese)". Maybe because she's beautiful, lovely and lively, as well as processing inhuman powers. Too bad she didn't get an deserved ending of "They're happy after ever".
If you don't know the original cartoonist Naru Nanao (七尾奈留), face portrait of Chairman Mao and rethink your life. She's one of the most well-known cartoonist in Japan during past two decades and the one who designed characters for the milestone of visual novel "Da Capo".