There is a popclip plugin for Kagi already, which is cool
https://www.popclip.app/extensions/x/z9d8vd
An extension for Kagi Translate that opens results in a popup (not just open a browser window) would be a very nice touch.
Popclip lets you react to selected text across the OSX environment. There are already translation plugins for Reverso, DeepL, Google, and the OSX native translation, but some require you to have their software installed, or to pay, etc...
You simply select text, click the "Kagi translate" button, and get some popup of unknown size showing the translation based on auto-detected language, plus maybe a drop down to correct the language if the detection made a mistake.