。
It'd be nice if there were a Japanese version.
Literal
Japanese-language version [subject-が] existed [wish-たらいいな].
~たらいいな ('it would be nice if') is the wish pattern: conditional ~たら + いい + な (reflective). 日本語版 ('Japanese language version') is standard software/media vocabulary. A simple, widely relatable wish — anyone who's wanted localization has felt this.