Having a "Translate Page" dropdown like shown above makes sense, but a general translation service seems, to me, a bit out of scope for search.
I would probably use it if Kagi had it, but I have no issues using Google Translate or e.g. ChatGPT to translate text and I'm not sure how a general translation service fits into a search service. I'm not saying that's the only thing Kagi can or should be, but I personally would rather see focus on search with as little side-tracking as possible. If it's a quick and cheap thing to implement I don't see any issues though!