A common thing I would do on Google was look up "kg to lbs" or some other unit. This would of course give the answer of 2.2lbs, which is what's on Kagi, however Google also will pop up a little calculator to interactively let you play with numbers right away without mucking with the search bar.
I cannot imagine that this would be terribly hard? You're already detecting that it's a unit conversion, so I would think that all you have to do is load a quick little conversion widget.
The easiest example I can think of is to go to Google.com. Type "kg to lbs". Hit enter.
This will give the suggested answer of 2.2lbs, but also pop up a widget that allows the user to interactively play with the numbers without having to refresh or send a new request to do it.